Sync from Piper @316511779

PROTOBUF_SYNC_PIPER
diff --git a/CHANGES.txt b/CHANGES.txt
index 43be322..0f540f7 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,12 +1,42 @@
 Unreleased Changes
 
   C++:
+  * Removed deprecated unsafe arena string accessors
   * Enabled heterogeneous lookup for std::string keys in maps.
-  * Improved the randomness of map ordering.
+  * Removed implicit conversion from StringPiece to std::string
+  * Fix use-after-destroy bug when the Map is allocated in the arena.
+  * Improved the randomness of map ordering
+  * Added stack overflow protection for text format with unknown fields
+  * Use std::hash for proto maps to help with portability.
+  * Added more Windows macros to proto whitelist.
+  * Arena constructors for map entry messages are now marked "explicit"
+    (for regular messages they were already explicit).
 
   Python:
+  * Reject lowercase t for Timestamp json format. Fixes a conformance test.
   * Improved the error message when AttributeError is returned from __getattr__
     in EnumTypeWrapper.
+  * Json format will print full_name directly for extensions.
+
+  Java:
+  * Fixed a bug where setting optional proto3 enums with setFooValue() would
+    not mark the value as present.
+
+  C#:
+  * Dropped support for netstandard1.0 (replaced by support for netstandard1.1).
+    This was required to modernize the parsing stack to use the `Span<byte>`
+    type internally. (#7351)
+  * Add `ParseFrom(ReadOnlySequence<byte>)` method to enable GC friendly
+    parsing with reduced allocations and buffer copies. (#7351)
+  * Add `GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE` define to make
+    generated code compatible with old C# compilers (pre-roslyn compilers
+    from .NET framework and old versions of mono) that do not support
+    ref structs. (#7490)
+
+2020-06-01 version 3.12.3 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
+
+  Objective-C
+  * Tweak the union used for Extensions to support old generated code. #7573
 
 2020-05-26 version 3.12.2 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
 
diff --git a/Protobuf.podspec b/Protobuf.podspec
index a05b712..3b7a716 100644
--- a/Protobuf.podspec
+++ b/Protobuf.podspec
@@ -5,7 +5,7 @@
 # dependent projects use the :git notation to refer to the library.
 Pod::Spec.new do |s|
   s.name     = 'Protobuf'
-  s.version  = '3.12.2'
+  s.version  = '3.12.3'
   s.summary  = 'Protocol Buffers v.3 runtime library for Objective-C.'
   s.homepage = 'https://github.com/protocolbuffers/protobuf'
   s.license  = '3-Clause BSD License'
diff --git a/conformance/failure_list_csharp.txt b/conformance/failure_list_csharp.txt
index f82f0f2..31bdf25 100644
--- a/conformance/failure_list_csharp.txt
+++ b/conformance/failure_list_csharp.txt
@@ -1,4 +1,3 @@
 Recommended.Proto3.JsonInput.BytesFieldBase64Url.JsonOutput
 Recommended.Proto3.JsonInput.BytesFieldBase64Url.ProtobufOutput
-Required.Proto2.JsonInput.StoresDefaultPrimitive.Validator
 Recommended.Proto2.JsonInput.FieldNameExtension.Validator
diff --git a/conformance/failure_list_python.txt b/conformance/failure_list_python.txt
index 3f7a811..e69de29 100644
--- a/conformance/failure_list_python.txt
+++ b/conformance/failure_list_python.txt
@@ -1,30 +0,0 @@
-Recommended.Proto3.JsonInput.BytesFieldBase64Url.JsonOutput
-Recommended.Proto3.JsonInput.BytesFieldBase64Url.ProtobufOutput
-Recommended.Proto3.JsonInput.DoubleFieldInfinityNotQuoted
-Recommended.Proto3.JsonInput.DoubleFieldNanNotQuoted
-Recommended.Proto3.JsonInput.DoubleFieldNegativeInfinityNotQuoted
-Recommended.Proto3.JsonInput.FloatFieldInfinityNotQuoted
-Recommended.Proto3.JsonInput.FloatFieldNanNotQuoted
-Recommended.Proto3.JsonInput.FloatFieldNegativeInfinityNotQuoted
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.BOOL[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.BYTES[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.DOUBLE[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.ENUM[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.FIXED32[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.FIXED64[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.FLOAT[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.INT32[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.INT32[6].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.INT64[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.SFIXED32[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.SFIXED64[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.SINT32[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.SINT64[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.STRING[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.UINT32[0].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.UINT32[5].ProtobufOutput
-Recommended.Proto3.ProtobufInput.ValidDataScalarBinary.UINT64[0].ProtobufOutput
-Required.Proto3.JsonInput.DoubleFieldTooSmall
-Required.Proto3.JsonInput.FloatFieldTooLarge
-Required.Proto3.JsonInput.FloatFieldTooSmall
-Required.Proto3.JsonInput.RepeatedFieldWrongElementTypeExpectingIntegersGotBool
diff --git a/conformance/failure_list_python_cpp.txt b/conformance/failure_list_python_cpp.txt
index df16455..9efb6cf 100644
--- a/conformance/failure_list_python_cpp.txt
+++ b/conformance/failure_list_python_cpp.txt
@@ -6,16 +6,3 @@
 #
 # TODO(haberman): insert links to corresponding bugs tracking the issue.
 # Should we use GitHub issues or the Google-internal bug tracker?
-
-Recommended.Proto3.JsonInput.BytesFieldBase64Url.JsonOutput
-Recommended.Proto3.JsonInput.BytesFieldBase64Url.ProtobufOutput
-Recommended.Proto3.JsonInput.DoubleFieldInfinityNotQuoted
-Recommended.Proto3.JsonInput.DoubleFieldNanNotQuoted
-Recommended.Proto3.JsonInput.DoubleFieldNegativeInfinityNotQuoted
-Recommended.Proto3.JsonInput.FloatFieldInfinityNotQuoted
-Recommended.Proto3.JsonInput.FloatFieldNanNotQuoted
-Recommended.Proto3.JsonInput.FloatFieldNegativeInfinityNotQuoted
-Required.Proto3.JsonInput.DoubleFieldTooSmall
-Required.Proto3.JsonInput.FloatFieldTooLarge
-Required.Proto3.JsonInput.FloatFieldTooSmall
-Required.Proto3.JsonInput.RepeatedFieldWrongElementTypeExpectingIntegersGotBool
diff --git a/csharp/Google.Protobuf.Tools.nuspec b/csharp/Google.Protobuf.Tools.nuspec
index 50aca1b..d0c088f 100644
--- a/csharp/Google.Protobuf.Tools.nuspec
+++ b/csharp/Google.Protobuf.Tools.nuspec
@@ -5,7 +5,7 @@
     <title>Google Protocol Buffers tools</title>
     <summary>Tools for Protocol Buffers - Google's data interchange format.</summary>
     <description>See project site for more info.</description>
-    <version>3.12.2</version>
+    <version>3.12.3</version>
     <authors>Google Inc.</authors>
     <owners>protobuf-packages</owners>
     <licenseUrl>https://github.com/protocolbuffers/protobuf/blob/master/LICENSE</licenseUrl>
diff --git a/csharp/src/AddressBook/Addressbook.cs b/csharp/src/AddressBook/Addressbook.cs
index 3b1da4d..1b1c1b6 100644
--- a/csharp/src/AddressBook/Addressbook.cs
+++ b/csharp/src/AddressBook/Addressbook.cs
@@ -49,7 +49,11 @@
   /// <summary>
   /// [START messages]
   /// </summary>
-  public sealed partial class Person : pb::IMessage<Person>, pb::IBufferMessage {
+  public sealed partial class Person : pb::IMessage<Person>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Person> _parser = new pb::MessageParser<Person>(() => new Person());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -256,9 +260,44 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 16: {
+            Id = input.ReadInt32();
+            break;
+          }
+          case 26: {
+            Email = input.ReadString();
+            break;
+          }
+          case 34: {
+            phones_.AddEntriesFrom(input, _repeated_phones_codec);
+            break;
+          }
+          case 42: {
+            if (lastUpdated_ == null) {
+              LastUpdated = new global::Google.Protobuf.WellKnownTypes.Timestamp();
+            }
+            input.ReadMessage(LastUpdated);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -293,6 +332,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the Person message type.</summary>
@@ -304,7 +344,11 @@
         [pbr::OriginalName("WORK")] Work = 2,
       }
 
-      public sealed partial class PhoneNumber : pb::IMessage<PhoneNumber>, pb::IBufferMessage {
+      public sealed partial class PhoneNumber : pb::IMessage<PhoneNumber>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<PhoneNumber> _parser = new pb::MessageParser<PhoneNumber>(() => new PhoneNumber());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -441,9 +485,29 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 10: {
+                Number = input.ReadString();
+                break;
+              }
+              case 16: {
+                Type = (global::Google.Protobuf.Examples.AddressBook.Person.Types.PhoneType) input.ReadEnum();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -463,6 +527,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -474,7 +539,11 @@
   /// <summary>
   /// Our address book file is just one of these.
   /// </summary>
-  public sealed partial class AddressBook : pb::IMessage<AddressBook>, pb::IBufferMessage {
+  public sealed partial class AddressBook : pb::IMessage<AddressBook>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<AddressBook> _parser = new pb::MessageParser<AddressBook>(() => new AddressBook());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -579,9 +648,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            people_.AddEntriesFrom(input, _repeated_people_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -597,6 +682,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Benchmarks/BenchmarkMessage1Proto3.cs b/csharp/src/Google.Protobuf.Benchmarks/BenchmarkMessage1Proto3.cs
index 291a585..6a21334 100644
--- a/csharp/src/Google.Protobuf.Benchmarks/BenchmarkMessage1Proto3.cs
+++ b/csharp/src/Google.Protobuf.Benchmarks/BenchmarkMessage1Proto3.cs
@@ -64,7 +64,11 @@
 
   }
   #region Messages
-  public sealed partial class GoogleMessage1 : pb::IMessage<GoogleMessage1>, pb::IBufferMessage {
+  public sealed partial class GoogleMessage1 : pb::IMessage<GoogleMessage1>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<GoogleMessage1> _parser = new pb::MessageParser<GoogleMessage1>(() => new GoogleMessage1());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1132,9 +1136,189 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Field1 = input.ReadString();
+            break;
+          }
+          case 16: {
+            Field2 = input.ReadInt32();
+            break;
+          }
+          case 24: {
+            Field3 = input.ReadInt32();
+            break;
+          }
+          case 34: {
+            Field4 = input.ReadString();
+            break;
+          }
+          case 42:
+          case 41: {
+            field5_.AddEntriesFrom(input, _repeated_field5_codec);
+            break;
+          }
+          case 48: {
+            Field6 = input.ReadInt32();
+            break;
+          }
+          case 58: {
+            Field7 = input.ReadString();
+            break;
+          }
+          case 74: {
+            Field9 = input.ReadString();
+            break;
+          }
+          case 96: {
+            Field12 = input.ReadBool();
+            break;
+          }
+          case 104: {
+            Field13 = input.ReadBool();
+            break;
+          }
+          case 112: {
+            Field14 = input.ReadBool();
+            break;
+          }
+          case 122: {
+            if (field15_ == null) {
+              Field15 = new global::Benchmarks.Proto3.GoogleMessage1SubMessage();
+            }
+            input.ReadMessage(Field15);
+            break;
+          }
+          case 128: {
+            Field16 = input.ReadInt32();
+            break;
+          }
+          case 136: {
+            Field17 = input.ReadBool();
+            break;
+          }
+          case 146: {
+            Field18 = input.ReadString();
+            break;
+          }
+          case 176: {
+            Field22 = input.ReadInt64();
+            break;
+          }
+          case 184: {
+            Field23 = input.ReadInt32();
+            break;
+          }
+          case 192: {
+            Field24 = input.ReadBool();
+            break;
+          }
+          case 200: {
+            Field25 = input.ReadInt32();
+            break;
+          }
+          case 232: {
+            Field29 = input.ReadInt32();
+            break;
+          }
+          case 240: {
+            Field30 = input.ReadBool();
+            break;
+          }
+          case 472: {
+            Field59 = input.ReadBool();
+            break;
+          }
+          case 480: {
+            Field60 = input.ReadInt32();
+            break;
+          }
+          case 536: {
+            Field67 = input.ReadInt32();
+            break;
+          }
+          case 544: {
+            Field68 = input.ReadInt32();
+            break;
+          }
+          case 624: {
+            Field78 = input.ReadBool();
+            break;
+          }
+          case 640: {
+            Field80 = input.ReadBool();
+            break;
+          }
+          case 648: {
+            Field81 = input.ReadBool();
+            break;
+          }
+          case 800: {
+            Field100 = input.ReadInt32();
+            break;
+          }
+          case 808: {
+            Field101 = input.ReadInt32();
+            break;
+          }
+          case 818: {
+            Field102 = input.ReadString();
+            break;
+          }
+          case 826: {
+            Field103 = input.ReadString();
+            break;
+          }
+          case 832: {
+            Field104 = input.ReadInt32();
+            break;
+          }
+          case 1024: {
+            Field128 = input.ReadInt32();
+            break;
+          }
+          case 1034: {
+            Field129 = input.ReadString();
+            break;
+          }
+          case 1040: {
+            Field130 = input.ReadInt32();
+            break;
+          }
+          case 1048: {
+            Field131 = input.ReadInt32();
+            break;
+          }
+          case 1200: {
+            Field150 = input.ReadInt32();
+            break;
+          }
+          case 2168: {
+            Field271 = input.ReadInt32();
+            break;
+          }
+          case 2176: {
+            Field272 = input.ReadInt32();
+            break;
+          }
+          case 2240: {
+            Field280 = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1314,10 +1498,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class GoogleMessage1SubMessage : pb::IMessage<GoogleMessage1SubMessage>, pb::IBufferMessage {
+  public sealed partial class GoogleMessage1SubMessage : pb::IMessage<GoogleMessage1SubMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<GoogleMessage1SubMessage> _parser = new pb::MessageParser<GoogleMessage1SubMessage>(() => new GoogleMessage1SubMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1886,9 +2075,101 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Field1 = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            Field2 = input.ReadInt32();
+            break;
+          }
+          case 24: {
+            Field3 = input.ReadInt32();
+            break;
+          }
+          case 96: {
+            Field12 = input.ReadBool();
+            break;
+          }
+          case 104: {
+            Field13 = input.ReadInt64();
+            break;
+          }
+          case 112: {
+            Field14 = input.ReadInt64();
+            break;
+          }
+          case 122: {
+            Field15 = input.ReadString();
+            break;
+          }
+          case 128: {
+            Field16 = input.ReadInt32();
+            break;
+          }
+          case 152: {
+            Field19 = input.ReadInt32();
+            break;
+          }
+          case 160: {
+            Field20 = input.ReadBool();
+            break;
+          }
+          case 169: {
+            Field21 = input.ReadFixed64();
+            break;
+          }
+          case 176: {
+            Field22 = input.ReadInt32();
+            break;
+          }
+          case 184: {
+            Field23 = input.ReadBool();
+            break;
+          }
+          case 224: {
+            Field28 = input.ReadBool();
+            break;
+          }
+          case 1629: {
+            Field203 = input.ReadFixed32();
+            break;
+          }
+          case 1632: {
+            Field204 = input.ReadInt32();
+            break;
+          }
+          case 1642: {
+            Field205 = input.ReadString();
+            break;
+          }
+          case 1648: {
+            Field206 = input.ReadBool();
+            break;
+          }
+          case 1656: {
+            Field207 = input.ReadUInt64();
+            break;
+          }
+          case 2400: {
+            Field300 = input.ReadUInt64();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1980,6 +2261,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Benchmarks/Benchmarks.cs b/csharp/src/Google.Protobuf.Benchmarks/Benchmarks.cs
index 456edbf..ce2248a 100644
--- a/csharp/src/Google.Protobuf.Benchmarks/Benchmarks.cs
+++ b/csharp/src/Google.Protobuf.Benchmarks/Benchmarks.cs
@@ -38,7 +38,11 @@
 
   }
   #region Messages
-  public sealed partial class BenchmarkDataset : pb::IMessage<BenchmarkDataset>, pb::IBufferMessage {
+  public sealed partial class BenchmarkDataset : pb::IMessage<BenchmarkDataset>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<BenchmarkDataset> _parser = new pb::MessageParser<BenchmarkDataset>(() => new BenchmarkDataset());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -219,9 +223,33 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            MessageName = input.ReadString();
+            break;
+          }
+          case 26: {
+            payload_.AddEntriesFrom(input, _repeated_payload_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -245,6 +273,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Benchmarks/ParseMessagesBenchmark.cs b/csharp/src/Google.Protobuf.Benchmarks/ParseMessagesBenchmark.cs
index 30f3e9e..92c3dbe 100644
--- a/csharp/src/Google.Protobuf.Benchmarks/ParseMessagesBenchmark.cs
+++ b/csharp/src/Google.Protobuf.Benchmarks/ParseMessagesBenchmark.cs
@@ -37,6 +37,7 @@
 using System.Linq;
 using System.Buffers;
 using Google.Protobuf.WellKnownTypes;
+using Benchmarks.Proto3;
 
 namespace Google.Protobuf.Benchmarks
 {
@@ -50,6 +51,7 @@
 
         SubTest manyWrapperFieldsTest = new SubTest(CreateManyWrapperFieldsMessage(), ManyWrapperFieldsMessage.Parser, () => new ManyWrapperFieldsMessage(), MaxMessages);
         SubTest manyPrimitiveFieldsTest = new SubTest(CreateManyPrimitiveFieldsMessage(), ManyPrimitiveFieldsMessage.Parser, () => new ManyPrimitiveFieldsMessage(), MaxMessages);
+        SubTest repeatedFieldTest = new SubTest(CreateRepeatedFieldMessage(), GoogleMessage1.Parser, () => new GoogleMessage1(), MaxMessages);
         SubTest emptyMessageTest = new SubTest(new Empty(), Empty.Parser, () => new Empty(), MaxMessages);
 
         public IEnumerable<int> MessageCountValues => new[] { 10, 100 };
@@ -84,6 +86,18 @@
         }
 
         [Benchmark]
+        public IMessage RepeatedFieldMessage_ParseFromByteArray()
+        {
+            return repeatedFieldTest.ParseFromByteArray();
+        }
+
+        [Benchmark]
+        public IMessage RepeatedFieldMessage_ParseFromReadOnlySequence()
+        {
+            return repeatedFieldTest.ParseFromReadOnlySequence();
+        }
+
+        [Benchmark]
         public IMessage EmptyMessage_ParseFromByteArray()
         {
             return emptyMessageTest.ParseFromByteArray();
@@ -123,6 +137,20 @@
             manyPrimitiveFieldsTest.ParseDelimitedMessagesFromReadOnlySequence(messageCount);
         }
 
+        [Benchmark]
+        [ArgumentsSource(nameof(MessageCountValues))]
+        public void RepeatedFieldMessage_ParseDelimitedMessagesFromByteArray(int messageCount)
+        {
+            repeatedFieldTest.ParseDelimitedMessagesFromByteArray(messageCount);
+        }
+
+        [Benchmark]
+        [ArgumentsSource(nameof(MessageCountValues))]
+        public void RepeatedFieldMessage_ParseDelimitedMessagesFromReadOnlySequence(int messageCount)
+        {
+            repeatedFieldTest.ParseDelimitedMessagesFromReadOnlySequence(messageCount);
+        }
+
         private static ManyWrapperFieldsMessage CreateManyWrapperFieldsMessage()
         {
             // Example data match data of an internal benchmarks
@@ -157,6 +185,17 @@
             };
         }
 
+        private static GoogleMessage1 CreateRepeatedFieldMessage()
+        {
+            // Message with a repeated fixed length item collection
+            var message = new GoogleMessage1();
+            for (ulong i = 0; i < 1000; i++)
+            {
+                message.Field5.Add(i);
+            }
+            return message;
+        }
+
         private class SubTest
         {
             private readonly IMessage message;
diff --git a/csharp/src/Google.Protobuf.Benchmarks/WrapperBenchmarkMessages.cs b/csharp/src/Google.Protobuf.Benchmarks/WrapperBenchmarkMessages.cs
index 76e95d6..95f613e 100644
--- a/csharp/src/Google.Protobuf.Benchmarks/WrapperBenchmarkMessages.cs
+++ b/csharp/src/Google.Protobuf.Benchmarks/WrapperBenchmarkMessages.cs
@@ -237,7 +237,11 @@
   /// a message that has a large number of wrapper fields
   /// obfuscated version of an internal message
   /// </summary>
-  public sealed partial class ManyWrapperFieldsMessage : pb::IMessage<ManyWrapperFieldsMessage>, pb::IBufferMessage {
+  public sealed partial class ManyWrapperFieldsMessage : pb::IMessage<ManyWrapperFieldsMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ManyWrapperFieldsMessage> _parser = new pb::MessageParser<ManyWrapperFieldsMessage>(() => new ManyWrapperFieldsMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3303,9 +3307,787 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            double? value = _single_doubleField1_codec.Read(input);
+            if (doubleField1_ == null || value != 0D) {
+              DoubleField1 = value;
+            }
+            break;
+          }
+          case 18: {
+            long? value = _single_int64Field2_codec.Read(input);
+            if (int64Field2_ == null || value != 0L) {
+              Int64Field2 = value;
+            }
+            break;
+          }
+          case 26: {
+            long? value = _single_int64Field3_codec.Read(input);
+            if (int64Field3_ == null || value != 0L) {
+              Int64Field3 = value;
+            }
+            break;
+          }
+          case 34: {
+            long? value = _single_int64Field4_codec.Read(input);
+            if (int64Field4_ == null || value != 0L) {
+              Int64Field4 = value;
+            }
+            break;
+          }
+          case 58: {
+            double? value = _single_doubleField7_codec.Read(input);
+            if (doubleField7_ == null || value != 0D) {
+              DoubleField7 = value;
+            }
+            break;
+          }
+          case 66: {
+            double? value = _single_doubleField8_codec.Read(input);
+            if (doubleField8_ == null || value != 0D) {
+              DoubleField8 = value;
+            }
+            break;
+          }
+          case 74: {
+            double? value = _single_doubleField9_codec.Read(input);
+            if (doubleField9_ == null || value != 0D) {
+              DoubleField9 = value;
+            }
+            break;
+          }
+          case 82: {
+            double? value = _single_doubleField10_codec.Read(input);
+            if (doubleField10_ == null || value != 0D) {
+              DoubleField10 = value;
+            }
+            break;
+          }
+          case 90: {
+            double? value = _single_doubleField11_codec.Read(input);
+            if (doubleField11_ == null || value != 0D) {
+              DoubleField11 = value;
+            }
+            break;
+          }
+          case 114: {
+            double? value = _single_doubleField14_codec.Read(input);
+            if (doubleField14_ == null || value != 0D) {
+              DoubleField14 = value;
+            }
+            break;
+          }
+          case 122: {
+            double? value = _single_doubleField15_codec.Read(input);
+            if (doubleField15_ == null || value != 0D) {
+              DoubleField15 = value;
+            }
+            break;
+          }
+          case 154: {
+            long? value = _single_int64Field19_codec.Read(input);
+            if (int64Field19_ == null || value != 0L) {
+              Int64Field19 = value;
+            }
+            break;
+          }
+          case 162: {
+            double? value = _single_doubleField20_codec.Read(input);
+            if (doubleField20_ == null || value != 0D) {
+              DoubleField20 = value;
+            }
+            break;
+          }
+          case 170: {
+            double? value = _single_doubleField21_codec.Read(input);
+            if (doubleField21_ == null || value != 0D) {
+              DoubleField21 = value;
+            }
+            break;
+          }
+          case 178: {
+            double? value = _single_doubleField22_codec.Read(input);
+            if (doubleField22_ == null || value != 0D) {
+              DoubleField22 = value;
+            }
+            break;
+          }
+          case 202: {
+            double? value = _single_doubleField25_codec.Read(input);
+            if (doubleField25_ == null || value != 0D) {
+              DoubleField25 = value;
+            }
+            break;
+          }
+          case 210: {
+            long? value = _single_int64Field26_codec.Read(input);
+            if (int64Field26_ == null || value != 0L) {
+              Int64Field26 = value;
+            }
+            break;
+          }
+          case 226: {
+            double? value = _single_doubleField28_codec.Read(input);
+            if (doubleField28_ == null || value != 0D) {
+              DoubleField28 = value;
+            }
+            break;
+          }
+          case 234: {
+            double? value = _single_doubleField29_codec.Read(input);
+            if (doubleField29_ == null || value != 0D) {
+              DoubleField29 = value;
+            }
+            break;
+          }
+          case 242: {
+            double? value = _single_doubleField30_codec.Read(input);
+            if (doubleField30_ == null || value != 0D) {
+              DoubleField30 = value;
+            }
+            break;
+          }
+          case 250: {
+            double? value = _single_doubleField31_codec.Read(input);
+            if (doubleField31_ == null || value != 0D) {
+              DoubleField31 = value;
+            }
+            break;
+          }
+          case 258: {
+            long? value = _single_int64Field32_codec.Read(input);
+            if (int64Field32_ == null || value != 0L) {
+              Int64Field32 = value;
+            }
+            break;
+          }
+          case 298: {
+            long? value = _single_int64Field37_codec.Read(input);
+            if (int64Field37_ == null || value != 0L) {
+              Int64Field37 = value;
+            }
+            break;
+          }
+          case 306: {
+            double? value = _single_doubleField38_codec.Read(input);
+            if (doubleField38_ == null || value != 0D) {
+              DoubleField38 = value;
+            }
+            break;
+          }
+          case 314: {
+            long? value = _single_interactions_codec.Read(input);
+            if (interactions_ == null || value != 0L) {
+              Interactions = value;
+            }
+            break;
+          }
+          case 322: {
+            double? value = _single_doubleField40_codec.Read(input);
+            if (doubleField40_ == null || value != 0D) {
+              DoubleField40 = value;
+            }
+            break;
+          }
+          case 330: {
+            long? value = _single_int64Field41_codec.Read(input);
+            if (int64Field41_ == null || value != 0L) {
+              Int64Field41 = value;
+            }
+            break;
+          }
+          case 338: {
+            double? value = _single_doubleField42_codec.Read(input);
+            if (doubleField42_ == null || value != 0D) {
+              DoubleField42 = value;
+            }
+            break;
+          }
+          case 346: {
+            long? value = _single_int64Field43_codec.Read(input);
+            if (int64Field43_ == null || value != 0L) {
+              Int64Field43 = value;
+            }
+            break;
+          }
+          case 354: {
+            long? value = _single_int64Field44_codec.Read(input);
+            if (int64Field44_ == null || value != 0L) {
+              Int64Field44 = value;
+            }
+            break;
+          }
+          case 362: {
+            double? value = _single_doubleField45_codec.Read(input);
+            if (doubleField45_ == null || value != 0D) {
+              DoubleField45 = value;
+            }
+            break;
+          }
+          case 370: {
+            double? value = _single_doubleField46_codec.Read(input);
+            if (doubleField46_ == null || value != 0D) {
+              DoubleField46 = value;
+            }
+            break;
+          }
+          case 378: {
+            double? value = _single_doubleField47_codec.Read(input);
+            if (doubleField47_ == null || value != 0D) {
+              DoubleField47 = value;
+            }
+            break;
+          }
+          case 386: {
+            double? value = _single_doubleField48_codec.Read(input);
+            if (doubleField48_ == null || value != 0D) {
+              DoubleField48 = value;
+            }
+            break;
+          }
+          case 394: {
+            double? value = _single_doubleField49_codec.Read(input);
+            if (doubleField49_ == null || value != 0D) {
+              DoubleField49 = value;
+            }
+            break;
+          }
+          case 402: {
+            double? value = _single_doubleField50_codec.Read(input);
+            if (doubleField50_ == null || value != 0D) {
+              DoubleField50 = value;
+            }
+            break;
+          }
+          case 410: {
+            double? value = _single_doubleField51_codec.Read(input);
+            if (doubleField51_ == null || value != 0D) {
+              DoubleField51 = value;
+            }
+            break;
+          }
+          case 418: {
+            double? value = _single_doubleField52_codec.Read(input);
+            if (doubleField52_ == null || value != 0D) {
+              DoubleField52 = value;
+            }
+            break;
+          }
+          case 426: {
+            double? value = _single_doubleField53_codec.Read(input);
+            if (doubleField53_ == null || value != 0D) {
+              DoubleField53 = value;
+            }
+            break;
+          }
+          case 434: {
+            double? value = _single_doubleField54_codec.Read(input);
+            if (doubleField54_ == null || value != 0D) {
+              DoubleField54 = value;
+            }
+            break;
+          }
+          case 442: {
+            double? value = _single_doubleField55_codec.Read(input);
+            if (doubleField55_ == null || value != 0D) {
+              DoubleField55 = value;
+            }
+            break;
+          }
+          case 450: {
+            double? value = _single_doubleField56_codec.Read(input);
+            if (doubleField56_ == null || value != 0D) {
+              DoubleField56 = value;
+            }
+            break;
+          }
+          case 458: {
+            double? value = _single_doubleField57_codec.Read(input);
+            if (doubleField57_ == null || value != 0D) {
+              DoubleField57 = value;
+            }
+            break;
+          }
+          case 466: {
+            double? value = _single_doubleField58_codec.Read(input);
+            if (doubleField58_ == null || value != 0D) {
+              DoubleField58 = value;
+            }
+            break;
+          }
+          case 474: {
+            long? value = _single_int64Field59_codec.Read(input);
+            if (int64Field59_ == null || value != 0L) {
+              Int64Field59 = value;
+            }
+            break;
+          }
+          case 482: {
+            long? value = _single_int64Field60_codec.Read(input);
+            if (int64Field60_ == null || value != 0L) {
+              Int64Field60 = value;
+            }
+            break;
+          }
+          case 498: {
+            double? value = _single_doubleField62_codec.Read(input);
+            if (doubleField62_ == null || value != 0D) {
+              DoubleField62 = value;
+            }
+            break;
+          }
+          case 522: {
+            double? value = _single_doubleField65_codec.Read(input);
+            if (doubleField65_ == null || value != 0D) {
+              DoubleField65 = value;
+            }
+            break;
+          }
+          case 530: {
+            double? value = _single_doubleField66_codec.Read(input);
+            if (doubleField66_ == null || value != 0D) {
+              DoubleField66 = value;
+            }
+            break;
+          }
+          case 538: {
+            double? value = _single_doubleField67_codec.Read(input);
+            if (doubleField67_ == null || value != 0D) {
+              DoubleField67 = value;
+            }
+            break;
+          }
+          case 546: {
+            double? value = _single_doubleField68_codec.Read(input);
+            if (doubleField68_ == null || value != 0D) {
+              DoubleField68 = value;
+            }
+            break;
+          }
+          case 554: {
+            double? value = _single_doubleField69_codec.Read(input);
+            if (doubleField69_ == null || value != 0D) {
+              DoubleField69 = value;
+            }
+            break;
+          }
+          case 562: {
+            double? value = _single_doubleField70_codec.Read(input);
+            if (doubleField70_ == null || value != 0D) {
+              DoubleField70 = value;
+            }
+            break;
+          }
+          case 570: {
+            double? value = _single_doubleField71_codec.Read(input);
+            if (doubleField71_ == null || value != 0D) {
+              DoubleField71 = value;
+            }
+            break;
+          }
+          case 578: {
+            double? value = _single_doubleField72_codec.Read(input);
+            if (doubleField72_ == null || value != 0D) {
+              DoubleField72 = value;
+            }
+            break;
+          }
+          case 586: {
+            string value = _single_stringField73_codec.Read(input);
+            if (stringField73_ == null || value != "") {
+              StringField73 = value;
+            }
+            break;
+          }
+          case 594: {
+            string value = _single_stringField74_codec.Read(input);
+            if (stringField74_ == null || value != "") {
+              StringField74 = value;
+            }
+            break;
+          }
+          case 602: {
+            double? value = _single_doubleField75_codec.Read(input);
+            if (doubleField75_ == null || value != 0D) {
+              DoubleField75 = value;
+            }
+            break;
+          }
+          case 618: {
+            double? value = _single_doubleField77_codec.Read(input);
+            if (doubleField77_ == null || value != 0D) {
+              DoubleField77 = value;
+            }
+            break;
+          }
+          case 626: {
+            double? value = _single_doubleField78_codec.Read(input);
+            if (doubleField78_ == null || value != 0D) {
+              DoubleField78 = value;
+            }
+            break;
+          }
+          case 634: {
+            double? value = _single_doubleField79_codec.Read(input);
+            if (doubleField79_ == null || value != 0D) {
+              DoubleField79 = value;
+            }
+            break;
+          }
+          case 640: {
+            EnumField80 = input.ReadInt32();
+            break;
+          }
+          case 648: {
+            EnumField81 = input.ReadInt32();
+            break;
+          }
+          case 658: {
+            long? value = _single_int64Field82_codec.Read(input);
+            if (int64Field82_ == null || value != 0L) {
+              Int64Field82 = value;
+            }
+            break;
+          }
+          case 664: {
+            EnumField83 = input.ReadInt32();
+            break;
+          }
+          case 674: {
+            double? value = _single_doubleField84_codec.Read(input);
+            if (doubleField84_ == null || value != 0D) {
+              DoubleField84 = value;
+            }
+            break;
+          }
+          case 682: {
+            long? value = _single_int64Field85_codec.Read(input);
+            if (int64Field85_ == null || value != 0L) {
+              Int64Field85 = value;
+            }
+            break;
+          }
+          case 690: {
+            long? value = _single_int64Field86_codec.Read(input);
+            if (int64Field86_ == null || value != 0L) {
+              Int64Field86 = value;
+            }
+            break;
+          }
+          case 698: {
+            long? value = _single_int64Field87_codec.Read(input);
+            if (int64Field87_ == null || value != 0L) {
+              Int64Field87 = value;
+            }
+            break;
+          }
+          case 706: {
+            double? value = _single_doubleField88_codec.Read(input);
+            if (doubleField88_ == null || value != 0D) {
+              DoubleField88 = value;
+            }
+            break;
+          }
+          case 714: {
+            double? value = _single_doubleField89_codec.Read(input);
+            if (doubleField89_ == null || value != 0D) {
+              DoubleField89 = value;
+            }
+            break;
+          }
+          case 722: {
+            double? value = _single_doubleField90_codec.Read(input);
+            if (doubleField90_ == null || value != 0D) {
+              DoubleField90 = value;
+            }
+            break;
+          }
+          case 730: {
+            double? value = _single_doubleField91_codec.Read(input);
+            if (doubleField91_ == null || value != 0D) {
+              DoubleField91 = value;
+            }
+            break;
+          }
+          case 738: {
+            double? value = _single_doubleField92_codec.Read(input);
+            if (doubleField92_ == null || value != 0D) {
+              DoubleField92 = value;
+            }
+            break;
+          }
+          case 746: {
+            double? value = _single_doubleField93_codec.Read(input);
+            if (doubleField93_ == null || value != 0D) {
+              DoubleField93 = value;
+            }
+            break;
+          }
+          case 754: {
+            double? value = _single_doubleField94_codec.Read(input);
+            if (doubleField94_ == null || value != 0D) {
+              DoubleField94 = value;
+            }
+            break;
+          }
+          case 762: {
+            double? value = _single_doubleField95_codec.Read(input);
+            if (doubleField95_ == null || value != 0D) {
+              DoubleField95 = value;
+            }
+            break;
+          }
+          case 770: {
+            double? value = _single_doubleField96_codec.Read(input);
+            if (doubleField96_ == null || value != 0D) {
+              DoubleField96 = value;
+            }
+            break;
+          }
+          case 778: {
+            double? value = _single_doubleField97_codec.Read(input);
+            if (doubleField97_ == null || value != 0D) {
+              DoubleField97 = value;
+            }
+            break;
+          }
+          case 786: {
+            double? value = _single_doubleField98_codec.Read(input);
+            if (doubleField98_ == null || value != 0D) {
+              DoubleField98 = value;
+            }
+            break;
+          }
+          case 794: {
+            double? value = _single_doubleField99_codec.Read(input);
+            if (doubleField99_ == null || value != 0D) {
+              DoubleField99 = value;
+            }
+            break;
+          }
+          case 802:
+          case 800: {
+            repeatedIntField100_.AddEntriesFrom(input, _repeated_repeatedIntField100_codec);
+            break;
+          }
+          case 810: {
+            double? value = _single_doubleField101_codec.Read(input);
+            if (doubleField101_ == null || value != 0D) {
+              DoubleField101 = value;
+            }
+            break;
+          }
+          case 818: {
+            double? value = _single_doubleField102_codec.Read(input);
+            if (doubleField102_ == null || value != 0D) {
+              DoubleField102 = value;
+            }
+            break;
+          }
+          case 826: {
+            double? value = _single_doubleField103_codec.Read(input);
+            if (doubleField103_ == null || value != 0D) {
+              DoubleField103 = value;
+            }
+            break;
+          }
+          case 834: {
+            double? value = _single_doubleField104_codec.Read(input);
+            if (doubleField104_ == null || value != 0D) {
+              DoubleField104 = value;
+            }
+            break;
+          }
+          case 842: {
+            double? value = _single_doubleField105_codec.Read(input);
+            if (doubleField105_ == null || value != 0D) {
+              DoubleField105 = value;
+            }
+            break;
+          }
+          case 850: {
+            double? value = _single_doubleField106_codec.Read(input);
+            if (doubleField106_ == null || value != 0D) {
+              DoubleField106 = value;
+            }
+            break;
+          }
+          case 858: {
+            long? value = _single_int64Field107_codec.Read(input);
+            if (int64Field107_ == null || value != 0L) {
+              Int64Field107 = value;
+            }
+            break;
+          }
+          case 866: {
+            double? value = _single_doubleField108_codec.Read(input);
+            if (doubleField108_ == null || value != 0D) {
+              DoubleField108 = value;
+            }
+            break;
+          }
+          case 874: {
+            double? value = _single_doubleField109_codec.Read(input);
+            if (doubleField109_ == null || value != 0D) {
+              DoubleField109 = value;
+            }
+            break;
+          }
+          case 882: {
+            long? value = _single_int64Field110_codec.Read(input);
+            if (int64Field110_ == null || value != 0L) {
+              Int64Field110 = value;
+            }
+            break;
+          }
+          case 890: {
+            double? value = _single_doubleField111_codec.Read(input);
+            if (doubleField111_ == null || value != 0D) {
+              DoubleField111 = value;
+            }
+            break;
+          }
+          case 898: {
+            long? value = _single_int64Field112_codec.Read(input);
+            if (int64Field112_ == null || value != 0L) {
+              Int64Field112 = value;
+            }
+            break;
+          }
+          case 906: {
+            double? value = _single_doubleField113_codec.Read(input);
+            if (doubleField113_ == null || value != 0D) {
+              DoubleField113 = value;
+            }
+            break;
+          }
+          case 914: {
+            long? value = _single_int64Field114_codec.Read(input);
+            if (int64Field114_ == null || value != 0L) {
+              Int64Field114 = value;
+            }
+            break;
+          }
+          case 922: {
+            long? value = _single_int64Field115_codec.Read(input);
+            if (int64Field115_ == null || value != 0L) {
+              Int64Field115 = value;
+            }
+            break;
+          }
+          case 930: {
+            double? value = _single_doubleField116_codec.Read(input);
+            if (doubleField116_ == null || value != 0D) {
+              DoubleField116 = value;
+            }
+            break;
+          }
+          case 938: {
+            long? value = _single_int64Field117_codec.Read(input);
+            if (int64Field117_ == null || value != 0L) {
+              Int64Field117 = value;
+            }
+            break;
+          }
+          case 946: {
+            double? value = _single_doubleField118_codec.Read(input);
+            if (doubleField118_ == null || value != 0D) {
+              DoubleField118 = value;
+            }
+            break;
+          }
+          case 954: {
+            double? value = _single_doubleField119_codec.Read(input);
+            if (doubleField119_ == null || value != 0D) {
+              DoubleField119 = value;
+            }
+            break;
+          }
+          case 962: {
+            double? value = _single_doubleField120_codec.Read(input);
+            if (doubleField120_ == null || value != 0D) {
+              DoubleField120 = value;
+            }
+            break;
+          }
+          case 970: {
+            double? value = _single_doubleField121_codec.Read(input);
+            if (doubleField121_ == null || value != 0D) {
+              DoubleField121 = value;
+            }
+            break;
+          }
+          case 978: {
+            double? value = _single_doubleField122_codec.Read(input);
+            if (doubleField122_ == null || value != 0D) {
+              DoubleField122 = value;
+            }
+            break;
+          }
+          case 986: {
+            double? value = _single_doubleField123_codec.Read(input);
+            if (doubleField123_ == null || value != 0D) {
+              DoubleField123 = value;
+            }
+            break;
+          }
+          case 994: {
+            double? value = _single_doubleField124_codec.Read(input);
+            if (doubleField124_ == null || value != 0D) {
+              DoubleField124 = value;
+            }
+            break;
+          }
+          case 1002: {
+            long? value = _single_int64Field125_codec.Read(input);
+            if (int64Field125_ == null || value != 0L) {
+              Int64Field125 = value;
+            }
+            break;
+          }
+          case 1010: {
+            long? value = _single_int64Field126_codec.Read(input);
+            if (int64Field126_ == null || value != 0L) {
+              Int64Field126 = value;
+            }
+            break;
+          }
+          case 1018: {
+            long? value = _single_int64Field127_codec.Read(input);
+            if (int64Field127_ == null || value != 0L) {
+              Int64Field127 = value;
+            }
+            break;
+          }
+          case 1026: {
+            double? value = _single_doubleField128_codec.Read(input);
+            if (doubleField128_ == null || value != 0D) {
+              DoubleField128 = value;
+            }
+            break;
+          }
+          case 1034: {
+            double? value = _single_doubleField129_codec.Read(input);
+            if (doubleField129_ == null || value != 0D) {
+              DoubleField129 = value;
+            }
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4083,6 +4865,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -4090,7 +4873,11 @@
   /// same as ManyWrapperFieldsMessages, but with primitive fields
   /// for comparison.
   /// </summary>
-  public sealed partial class ManyPrimitiveFieldsMessage : pb::IMessage<ManyPrimitiveFieldsMessage>, pb::IBufferMessage {
+  public sealed partial class ManyPrimitiveFieldsMessage : pb::IMessage<ManyPrimitiveFieldsMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ManyPrimitiveFieldsMessage> _parser = new pb::MessageParser<ManyPrimitiveFieldsMessage>(() => new ManyPrimitiveFieldsMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6835,9 +7622,466 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 9: {
+            DoubleField1 = input.ReadDouble();
+            break;
+          }
+          case 16: {
+            Int64Field2 = input.ReadInt64();
+            break;
+          }
+          case 24: {
+            Int64Field3 = input.ReadInt64();
+            break;
+          }
+          case 32: {
+            Int64Field4 = input.ReadInt64();
+            break;
+          }
+          case 57: {
+            DoubleField7 = input.ReadDouble();
+            break;
+          }
+          case 65: {
+            DoubleField8 = input.ReadDouble();
+            break;
+          }
+          case 73: {
+            DoubleField9 = input.ReadDouble();
+            break;
+          }
+          case 81: {
+            DoubleField10 = input.ReadDouble();
+            break;
+          }
+          case 89: {
+            DoubleField11 = input.ReadDouble();
+            break;
+          }
+          case 113: {
+            DoubleField14 = input.ReadDouble();
+            break;
+          }
+          case 121: {
+            DoubleField15 = input.ReadDouble();
+            break;
+          }
+          case 152: {
+            Int64Field19 = input.ReadInt64();
+            break;
+          }
+          case 161: {
+            DoubleField20 = input.ReadDouble();
+            break;
+          }
+          case 169: {
+            DoubleField21 = input.ReadDouble();
+            break;
+          }
+          case 177: {
+            DoubleField22 = input.ReadDouble();
+            break;
+          }
+          case 201: {
+            DoubleField25 = input.ReadDouble();
+            break;
+          }
+          case 208: {
+            Int64Field26 = input.ReadInt64();
+            break;
+          }
+          case 225: {
+            DoubleField28 = input.ReadDouble();
+            break;
+          }
+          case 233: {
+            DoubleField29 = input.ReadDouble();
+            break;
+          }
+          case 241: {
+            DoubleField30 = input.ReadDouble();
+            break;
+          }
+          case 249: {
+            DoubleField31 = input.ReadDouble();
+            break;
+          }
+          case 256: {
+            Int64Field32 = input.ReadInt64();
+            break;
+          }
+          case 296: {
+            Int64Field37 = input.ReadInt64();
+            break;
+          }
+          case 305: {
+            DoubleField38 = input.ReadDouble();
+            break;
+          }
+          case 312: {
+            Interactions = input.ReadInt64();
+            break;
+          }
+          case 321: {
+            DoubleField40 = input.ReadDouble();
+            break;
+          }
+          case 328: {
+            Int64Field41 = input.ReadInt64();
+            break;
+          }
+          case 337: {
+            DoubleField42 = input.ReadDouble();
+            break;
+          }
+          case 344: {
+            Int64Field43 = input.ReadInt64();
+            break;
+          }
+          case 352: {
+            Int64Field44 = input.ReadInt64();
+            break;
+          }
+          case 361: {
+            DoubleField45 = input.ReadDouble();
+            break;
+          }
+          case 369: {
+            DoubleField46 = input.ReadDouble();
+            break;
+          }
+          case 377: {
+            DoubleField47 = input.ReadDouble();
+            break;
+          }
+          case 385: {
+            DoubleField48 = input.ReadDouble();
+            break;
+          }
+          case 393: {
+            DoubleField49 = input.ReadDouble();
+            break;
+          }
+          case 401: {
+            DoubleField50 = input.ReadDouble();
+            break;
+          }
+          case 409: {
+            DoubleField51 = input.ReadDouble();
+            break;
+          }
+          case 417: {
+            DoubleField52 = input.ReadDouble();
+            break;
+          }
+          case 425: {
+            DoubleField53 = input.ReadDouble();
+            break;
+          }
+          case 433: {
+            DoubleField54 = input.ReadDouble();
+            break;
+          }
+          case 441: {
+            DoubleField55 = input.ReadDouble();
+            break;
+          }
+          case 449: {
+            DoubleField56 = input.ReadDouble();
+            break;
+          }
+          case 457: {
+            DoubleField57 = input.ReadDouble();
+            break;
+          }
+          case 465: {
+            DoubleField58 = input.ReadDouble();
+            break;
+          }
+          case 472: {
+            Int64Field59 = input.ReadInt64();
+            break;
+          }
+          case 480: {
+            Int64Field60 = input.ReadInt64();
+            break;
+          }
+          case 497: {
+            DoubleField62 = input.ReadDouble();
+            break;
+          }
+          case 521: {
+            DoubleField65 = input.ReadDouble();
+            break;
+          }
+          case 529: {
+            DoubleField66 = input.ReadDouble();
+            break;
+          }
+          case 537: {
+            DoubleField67 = input.ReadDouble();
+            break;
+          }
+          case 545: {
+            DoubleField68 = input.ReadDouble();
+            break;
+          }
+          case 553: {
+            DoubleField69 = input.ReadDouble();
+            break;
+          }
+          case 561: {
+            DoubleField70 = input.ReadDouble();
+            break;
+          }
+          case 569: {
+            DoubleField71 = input.ReadDouble();
+            break;
+          }
+          case 577: {
+            DoubleField72 = input.ReadDouble();
+            break;
+          }
+          case 586: {
+            StringField73 = input.ReadString();
+            break;
+          }
+          case 594: {
+            StringField74 = input.ReadString();
+            break;
+          }
+          case 601: {
+            DoubleField75 = input.ReadDouble();
+            break;
+          }
+          case 617: {
+            DoubleField77 = input.ReadDouble();
+            break;
+          }
+          case 625: {
+            DoubleField78 = input.ReadDouble();
+            break;
+          }
+          case 633: {
+            DoubleField79 = input.ReadDouble();
+            break;
+          }
+          case 640: {
+            EnumField80 = input.ReadInt32();
+            break;
+          }
+          case 648: {
+            EnumField81 = input.ReadInt32();
+            break;
+          }
+          case 656: {
+            Int64Field82 = input.ReadInt64();
+            break;
+          }
+          case 664: {
+            EnumField83 = input.ReadInt32();
+            break;
+          }
+          case 673: {
+            DoubleField84 = input.ReadDouble();
+            break;
+          }
+          case 680: {
+            Int64Field85 = input.ReadInt64();
+            break;
+          }
+          case 688: {
+            Int64Field86 = input.ReadInt64();
+            break;
+          }
+          case 696: {
+            Int64Field87 = input.ReadInt64();
+            break;
+          }
+          case 705: {
+            DoubleField88 = input.ReadDouble();
+            break;
+          }
+          case 713: {
+            DoubleField89 = input.ReadDouble();
+            break;
+          }
+          case 721: {
+            DoubleField90 = input.ReadDouble();
+            break;
+          }
+          case 729: {
+            DoubleField91 = input.ReadDouble();
+            break;
+          }
+          case 737: {
+            DoubleField92 = input.ReadDouble();
+            break;
+          }
+          case 745: {
+            DoubleField93 = input.ReadDouble();
+            break;
+          }
+          case 753: {
+            DoubleField94 = input.ReadDouble();
+            break;
+          }
+          case 761: {
+            DoubleField95 = input.ReadDouble();
+            break;
+          }
+          case 769: {
+            DoubleField96 = input.ReadDouble();
+            break;
+          }
+          case 777: {
+            DoubleField97 = input.ReadDouble();
+            break;
+          }
+          case 785: {
+            DoubleField98 = input.ReadDouble();
+            break;
+          }
+          case 793: {
+            DoubleField99 = input.ReadDouble();
+            break;
+          }
+          case 802:
+          case 800: {
+            repeatedIntField100_.AddEntriesFrom(input, _repeated_repeatedIntField100_codec);
+            break;
+          }
+          case 809: {
+            DoubleField101 = input.ReadDouble();
+            break;
+          }
+          case 817: {
+            DoubleField102 = input.ReadDouble();
+            break;
+          }
+          case 825: {
+            DoubleField103 = input.ReadDouble();
+            break;
+          }
+          case 833: {
+            DoubleField104 = input.ReadDouble();
+            break;
+          }
+          case 841: {
+            DoubleField105 = input.ReadDouble();
+            break;
+          }
+          case 849: {
+            DoubleField106 = input.ReadDouble();
+            break;
+          }
+          case 856: {
+            Int64Field107 = input.ReadInt64();
+            break;
+          }
+          case 865: {
+            DoubleField108 = input.ReadDouble();
+            break;
+          }
+          case 873: {
+            DoubleField109 = input.ReadDouble();
+            break;
+          }
+          case 880: {
+            Int64Field110 = input.ReadInt64();
+            break;
+          }
+          case 889: {
+            DoubleField111 = input.ReadDouble();
+            break;
+          }
+          case 896: {
+            Int64Field112 = input.ReadInt64();
+            break;
+          }
+          case 905: {
+            DoubleField113 = input.ReadDouble();
+            break;
+          }
+          case 912: {
+            Int64Field114 = input.ReadInt64();
+            break;
+          }
+          case 920: {
+            Int64Field115 = input.ReadInt64();
+            break;
+          }
+          case 929: {
+            DoubleField116 = input.ReadDouble();
+            break;
+          }
+          case 936: {
+            Int64Field117 = input.ReadInt64();
+            break;
+          }
+          case 945: {
+            DoubleField118 = input.ReadDouble();
+            break;
+          }
+          case 953: {
+            DoubleField119 = input.ReadDouble();
+            break;
+          }
+          case 961: {
+            DoubleField120 = input.ReadDouble();
+            break;
+          }
+          case 969: {
+            DoubleField121 = input.ReadDouble();
+            break;
+          }
+          case 977: {
+            DoubleField122 = input.ReadDouble();
+            break;
+          }
+          case 985: {
+            DoubleField123 = input.ReadDouble();
+            break;
+          }
+          case 993: {
+            DoubleField124 = input.ReadDouble();
+            break;
+          }
+          case 1000: {
+            Int64Field125 = input.ReadInt64();
+            break;
+          }
+          case 1008: {
+            Int64Field126 = input.ReadInt64();
+            break;
+          }
+          case 1016: {
+            Int64Field127 = input.ReadInt64();
+            break;
+          }
+          case 1025: {
+            DoubleField128 = input.ReadDouble();
+            break;
+          }
+          case 1033: {
+            DoubleField129 = input.ReadDouble();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -7294,6 +8538,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Conformance/Conformance.cs b/csharp/src/Google.Protobuf.Conformance/Conformance.cs
index f9bda13..2c08466 100644
--- a/csharp/src/Google.Protobuf.Conformance/Conformance.cs
+++ b/csharp/src/Google.Protobuf.Conformance/Conformance.cs
@@ -107,7 +107,11 @@
   /// This will be known by message_type == "conformance.FailureSet", a conformance
   /// test should return a serialized FailureSet in protobuf_payload.
   /// </summary>
-  public sealed partial class FailureSet : pb::IMessage<FailureSet>, pb::IBufferMessage {
+  public sealed partial class FailureSet : pb::IMessage<FailureSet>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FailureSet> _parser = new pb::MessageParser<FailureSet>(() => new FailureSet());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -212,9 +216,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            failure_.AddEntriesFrom(input, _repeated_failure_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -230,6 +250,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -240,7 +261,11 @@
   ///   2. parse the protobuf or JSON payload in "payload" (which may fail)
   ///   3. if the parse succeeded, serialize the message in the requested format.
   /// </summary>
-  public sealed partial class ConformanceRequest : pb::IMessage<ConformanceRequest>, pb::IBufferMessage {
+  public sealed partial class ConformanceRequest : pb::IMessage<ConformanceRequest>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ConformanceRequest> _parser = new pb::MessageParser<ConformanceRequest>(() => new ConformanceRequest());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -608,9 +633,60 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            ProtobufPayload = input.ReadBytes();
+            break;
+          }
+          case 18: {
+            JsonPayload = input.ReadString();
+            break;
+          }
+          case 24: {
+            RequestedOutputFormat = (global::Conformance.WireFormat) input.ReadEnum();
+            break;
+          }
+          case 34: {
+            MessageType = input.ReadString();
+            break;
+          }
+          case 40: {
+            TestCategory = (global::Conformance.TestCategory) input.ReadEnum();
+            break;
+          }
+          case 50: {
+            if (jspbEncodingOptions_ == null) {
+              JspbEncodingOptions = new global::Conformance.JspbEncodingConfig();
+            }
+            input.ReadMessage(JspbEncodingOptions);
+            break;
+          }
+          case 58: {
+            JspbPayload = input.ReadString();
+            break;
+          }
+          case 66: {
+            TextPayload = input.ReadString();
+            break;
+          }
+          case 72: {
+            PrintUnknownFields = input.ReadBool();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -661,13 +737,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Represents a single test case's output.
   /// </summary>
-  public sealed partial class ConformanceResponse : pb::IMessage<ConformanceResponse>, pb::IBufferMessage {
+  public sealed partial class ConformanceResponse : pb::IMessage<ConformanceResponse>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ConformanceResponse> _parser = new pb::MessageParser<ConformanceResponse>(() => new ConformanceResponse());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1035,9 +1116,53 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            ParseError = input.ReadString();
+            break;
+          }
+          case 18: {
+            RuntimeError = input.ReadString();
+            break;
+          }
+          case 26: {
+            ProtobufPayload = input.ReadBytes();
+            break;
+          }
+          case 34: {
+            JsonPayload = input.ReadString();
+            break;
+          }
+          case 42: {
+            Skipped = input.ReadString();
+            break;
+          }
+          case 50: {
+            SerializeError = input.ReadString();
+            break;
+          }
+          case 58: {
+            JspbPayload = input.ReadString();
+            break;
+          }
+          case 66: {
+            TextPayload = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1081,13 +1206,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Encoding options for jspb format.
   /// </summary>
-  public sealed partial class JspbEncodingConfig : pb::IMessage<JspbEncodingConfig>, pb::IBufferMessage {
+  public sealed partial class JspbEncodingConfig : pb::IMessage<JspbEncodingConfig>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<JspbEncodingConfig> _parser = new pb::MessageParser<JspbEncodingConfig>(() => new JspbEncodingConfig());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1203,9 +1333,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            UseJspbArrayAnyFormat = input.ReadBool();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1221,6 +1367,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Conformance/Program.cs b/csharp/src/Google.Protobuf.Conformance/Program.cs
index d1093ab..d721ecf 100644
--- a/csharp/src/Google.Protobuf.Conformance/Program.cs
+++ b/csharp/src/Google.Protobuf.Conformance/Program.cs
@@ -83,44 +83,52 @@
 
         private static ConformanceResponse PerformRequest(ConformanceRequest request, TypeRegistry typeRegistry)
         {
+            ExtensionRegistry proto2ExtensionRegistry = new ExtensionRegistry
+            {
+                ProtobufTestMessages.Proto2.TestMessagesProto2Extensions.ExtensionInt32,
+                ProtobufTestMessages.Proto2.TestAllTypesProto2.Types.MessageSetCorrectExtension1.Extensions.MessageSetExtension,
+                ProtobufTestMessages.Proto2.TestAllTypesProto2.Types.MessageSetCorrectExtension2.Extensions.MessageSetExtension
+            };
             IMessage message;
             try
             {
                 switch (request.PayloadCase)
                 {
                     case ConformanceRequest.PayloadOneofCase.JsonPayload:
-                        if (request.TestCategory == global::Conformance.TestCategory.JsonIgnoreUnknownParsingTest) {
+                        if (request.TestCategory == global::Conformance.TestCategory.JsonIgnoreUnknownParsingTest)
+                        {
                             return new ConformanceResponse { Skipped = "CSharp doesn't support skipping unknown fields in json parsing." };
                         }
                         var parser = new JsonParser(new JsonParser.Settings(20, typeRegistry));
-                        message = parser.Parse<ProtobufTestMessages.Proto3.TestAllTypesProto3>(request.JsonPayload);
+                        switch (request.MessageType)
+                        {
+                            case "protobuf_test_messages.proto3.TestAllTypesProto3":
+                                message = parser.Parse<ProtobufTestMessages.Proto3.TestAllTypesProto3>(request.JsonPayload);
+                                break;
+                            case "protobuf_test_messages.proto2.TestAllTypesProto2":
+                                message = parser.Parse<ProtobufTestMessages.Proto2.TestAllTypesProto2>(request.JsonPayload);
+                                break;
+                            default:
+                                throw new Exception($" Protobuf request doesn't have specific payload type ({request.MessageType})");
+                        }
                         break;
                     case ConformanceRequest.PayloadOneofCase.ProtobufPayload:
-                    {
-                        if (request.MessageType.Equals("protobuf_test_messages.proto3.TestAllTypesProto3"))
+                        switch (request.MessageType)
                         {
-                            message = ProtobufTestMessages.Proto3.TestAllTypesProto3.Parser.ParseFrom(request.ProtobufPayload);
-                        }
-                        else if (request.MessageType.Equals("protobuf_test_messages.proto2.TestAllTypesProto2"))
-                        {
-                            ExtensionRegistry registry = new ExtensionRegistry()
-                            {
-                                ProtobufTestMessages.Proto2.TestMessagesProto2Extensions.ExtensionInt32,
-                                ProtobufTestMessages.Proto2.TestAllTypesProto2.Types.MessageSetCorrectExtension1.Extensions.MessageSetExtension,
-                                ProtobufTestMessages.Proto2.TestAllTypesProto2.Types.MessageSetCorrectExtension2.Extensions.MessageSetExtension
-                            };
-                            message = ProtobufTestMessages.Proto2.TestAllTypesProto2.Parser.WithExtensionRegistry(registry).ParseFrom(request.ProtobufPayload);
-                        }
-                        else
-                        {
-                            throw new Exception(" Protobuf request doesn't have specific payload type");
+                            case "protobuf_test_messages.proto3.TestAllTypesProto3":
+                                message = ProtobufTestMessages.Proto3.TestAllTypesProto3.Parser.ParseFrom(request.ProtobufPayload);
+                                break;
+                            case "protobuf_test_messages.proto2.TestAllTypesProto2":
+                                message = ProtobufTestMessages.Proto2.TestAllTypesProto2.Parser
+                                    .WithExtensionRegistry(proto2ExtensionRegistry)
+                                    .ParseFrom(request.ProtobufPayload);
+                                break;
+                            default:
+                                throw new Exception($" Protobuf request doesn't have specific payload type ({request.MessageType})");
                         }
                         break;
-                    }
 					case ConformanceRequest.PayloadOneofCase.TextPayload:
-					{
 						return new ConformanceResponse { Skipped = "CSharp doesn't support text format" };
-					}
                     default:
                         throw new Exception("Unsupported request payload: " + request.PayloadCase);
                 }
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/MapUnittestProto3.cs b/csharp/src/Google.Protobuf.Test.TestProtos/MapUnittestProto3.cs
index 8d20605..308ccbd 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/MapUnittestProto3.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/MapUnittestProto3.cs
@@ -176,7 +176,11 @@
   /// <summary>
   /// Tests maps.
   /// </summary>
-  public sealed partial class TestMap : pb::IMessage<TestMap>, pb::IBufferMessage {
+  public sealed partial class TestMap : pb::IMessage<TestMap>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestMap> _parser = new pb::MessageParser<TestMap>(() => new TestMap());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -537,9 +541,89 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            mapInt32Int32_.AddEntriesFrom(input, _map_mapInt32Int32_codec);
+            break;
+          }
+          case 18: {
+            mapInt64Int64_.AddEntriesFrom(input, _map_mapInt64Int64_codec);
+            break;
+          }
+          case 26: {
+            mapUint32Uint32_.AddEntriesFrom(input, _map_mapUint32Uint32_codec);
+            break;
+          }
+          case 34: {
+            mapUint64Uint64_.AddEntriesFrom(input, _map_mapUint64Uint64_codec);
+            break;
+          }
+          case 42: {
+            mapSint32Sint32_.AddEntriesFrom(input, _map_mapSint32Sint32_codec);
+            break;
+          }
+          case 50: {
+            mapSint64Sint64_.AddEntriesFrom(input, _map_mapSint64Sint64_codec);
+            break;
+          }
+          case 58: {
+            mapFixed32Fixed32_.AddEntriesFrom(input, _map_mapFixed32Fixed32_codec);
+            break;
+          }
+          case 66: {
+            mapFixed64Fixed64_.AddEntriesFrom(input, _map_mapFixed64Fixed64_codec);
+            break;
+          }
+          case 74: {
+            mapSfixed32Sfixed32_.AddEntriesFrom(input, _map_mapSfixed32Sfixed32_codec);
+            break;
+          }
+          case 82: {
+            mapSfixed64Sfixed64_.AddEntriesFrom(input, _map_mapSfixed64Sfixed64_codec);
+            break;
+          }
+          case 90: {
+            mapInt32Float_.AddEntriesFrom(input, _map_mapInt32Float_codec);
+            break;
+          }
+          case 98: {
+            mapInt32Double_.AddEntriesFrom(input, _map_mapInt32Double_codec);
+            break;
+          }
+          case 106: {
+            mapBoolBool_.AddEntriesFrom(input, _map_mapBoolBool_codec);
+            break;
+          }
+          case 114: {
+            mapStringString_.AddEntriesFrom(input, _map_mapStringString_codec);
+            break;
+          }
+          case 122: {
+            mapInt32Bytes_.AddEntriesFrom(input, _map_mapInt32Bytes_codec);
+            break;
+          }
+          case 130: {
+            mapInt32Enum_.AddEntriesFrom(input, _map_mapInt32Enum_codec);
+            break;
+          }
+          case 138: {
+            mapInt32ForeignMessage_.AddEntriesFrom(input, _map_mapInt32ForeignMessage_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -619,10 +703,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestMapSubmessage : pb::IMessage<TestMapSubmessage>, pb::IBufferMessage {
+  public sealed partial class TestMapSubmessage : pb::IMessage<TestMapSubmessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestMapSubmessage> _parser = new pb::MessageParser<TestMapSubmessage>(() => new TestMapSubmessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -738,9 +827,28 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (testMap_ == null) {
+              TestMap = new global::Google.Protobuf.TestProtos.TestMap();
+            }
+            input.ReadMessage(TestMap);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -759,10 +867,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestMessageMap : pb::IMessage<TestMessageMap>, pb::IBufferMessage {
+  public sealed partial class TestMessageMap : pb::IMessage<TestMessageMap>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestMessageMap> _parser = new pb::MessageParser<TestMessageMap>(() => new TestMessageMap());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -867,9 +980,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            mapInt32Message_.AddEntriesFrom(input, _map_mapInt32Message_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -885,13 +1014,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Two map fields share the same entry default instance.
   /// </summary>
-  public sealed partial class TestSameTypeMap : pb::IMessage<TestSameTypeMap>, pb::IBufferMessage {
+  public sealed partial class TestSameTypeMap : pb::IMessage<TestSameTypeMap>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestSameTypeMap> _parser = new pb::MessageParser<TestSameTypeMap>(() => new TestSameTypeMap());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1012,9 +1146,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            map1_.AddEntriesFrom(input, _map_map1_codec);
+            break;
+          }
+          case 18: {
+            map2_.AddEntriesFrom(input, _map_map2_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1034,10 +1188,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestArenaMap : pb::IMessage<TestArenaMap>, pb::IBufferMessage {
+  public sealed partial class TestArenaMap : pb::IMessage<TestArenaMap>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestArenaMap> _parser = new pb::MessageParser<TestArenaMap>(() => new TestArenaMap());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1366,9 +1525,81 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            mapInt32Int32_.AddEntriesFrom(input, _map_mapInt32Int32_codec);
+            break;
+          }
+          case 18: {
+            mapInt64Int64_.AddEntriesFrom(input, _map_mapInt64Int64_codec);
+            break;
+          }
+          case 26: {
+            mapUint32Uint32_.AddEntriesFrom(input, _map_mapUint32Uint32_codec);
+            break;
+          }
+          case 34: {
+            mapUint64Uint64_.AddEntriesFrom(input, _map_mapUint64Uint64_codec);
+            break;
+          }
+          case 42: {
+            mapSint32Sint32_.AddEntriesFrom(input, _map_mapSint32Sint32_codec);
+            break;
+          }
+          case 50: {
+            mapSint64Sint64_.AddEntriesFrom(input, _map_mapSint64Sint64_codec);
+            break;
+          }
+          case 58: {
+            mapFixed32Fixed32_.AddEntriesFrom(input, _map_mapFixed32Fixed32_codec);
+            break;
+          }
+          case 66: {
+            mapFixed64Fixed64_.AddEntriesFrom(input, _map_mapFixed64Fixed64_codec);
+            break;
+          }
+          case 74: {
+            mapSfixed32Sfixed32_.AddEntriesFrom(input, _map_mapSfixed32Sfixed32_codec);
+            break;
+          }
+          case 82: {
+            mapSfixed64Sfixed64_.AddEntriesFrom(input, _map_mapSfixed64Sfixed64_codec);
+            break;
+          }
+          case 90: {
+            mapInt32Float_.AddEntriesFrom(input, _map_mapInt32Float_codec);
+            break;
+          }
+          case 98: {
+            mapInt32Double_.AddEntriesFrom(input, _map_mapInt32Double_codec);
+            break;
+          }
+          case 106: {
+            mapBoolBool_.AddEntriesFrom(input, _map_mapBoolBool_codec);
+            break;
+          }
+          case 114: {
+            mapInt32Enum_.AddEntriesFrom(input, _map_mapInt32Enum_codec);
+            break;
+          }
+          case 122: {
+            mapInt32ForeignMessage_.AddEntriesFrom(input, _map_mapInt32ForeignMessage_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1440,6 +1671,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -1447,7 +1679,11 @@
   /// Previously, message containing enum called Type cannot be used as value of
   /// map field.
   /// </summary>
-  public sealed partial class MessageContainingEnumCalledType : pb::IMessage<MessageContainingEnumCalledType>, pb::IBufferMessage {
+  public sealed partial class MessageContainingEnumCalledType : pb::IMessage<MessageContainingEnumCalledType>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<MessageContainingEnumCalledType> _parser = new pb::MessageParser<MessageContainingEnumCalledType>(() => new MessageContainingEnumCalledType());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1552,9 +1788,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            type_.AddEntriesFrom(input, _map_type_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1570,6 +1822,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the MessageContainingEnumCalledType message type.</summary>
@@ -1587,7 +1840,11 @@
   /// <summary>
   /// Previously, message cannot contain map field called "entry".
   /// </summary>
-  public sealed partial class MessageContainingMapCalledEntry : pb::IMessage<MessageContainingMapCalledEntry>, pb::IBufferMessage {
+  public sealed partial class MessageContainingMapCalledEntry : pb::IMessage<MessageContainingMapCalledEntry>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<MessageContainingMapCalledEntry> _parser = new pb::MessageParser<MessageContainingMapCalledEntry>(() => new MessageContainingMapCalledEntry());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1692,9 +1949,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            entry_.AddEntriesFrom(input, _map_entry_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1710,6 +1983,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/TestMessagesProto2.cs b/csharp/src/Google.Protobuf.Test.TestProtos/TestMessagesProto2.cs
index bef3645..eb22955 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/TestMessagesProto2.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/TestMessagesProto2.cs
@@ -244,7 +244,11 @@
   /// could trigger bugs that occur in any message type in this file.  We verify
   /// this stays true in a unit test.
   /// </summary>
-  public sealed partial class TestAllTypesProto2 : pb::IExtendableMessage<TestAllTypesProto2>, pb::IBufferMessage {
+  public sealed partial class TestAllTypesProto2 : pb::IExtendableMessage<TestAllTypesProto2>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestAllTypesProto2> _parser = new pb::MessageParser<TestAllTypesProto2>(() => new TestAllTypesProto2());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestAllTypesProto2> _extensions;
@@ -3311,9 +3315,556 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 8: {
+            OptionalInt32 = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            OptionalInt64 = input.ReadInt64();
+            break;
+          }
+          case 24: {
+            OptionalUint32 = input.ReadUInt32();
+            break;
+          }
+          case 32: {
+            OptionalUint64 = input.ReadUInt64();
+            break;
+          }
+          case 40: {
+            OptionalSint32 = input.ReadSInt32();
+            break;
+          }
+          case 48: {
+            OptionalSint64 = input.ReadSInt64();
+            break;
+          }
+          case 61: {
+            OptionalFixed32 = input.ReadFixed32();
+            break;
+          }
+          case 65: {
+            OptionalFixed64 = input.ReadFixed64();
+            break;
+          }
+          case 77: {
+            OptionalSfixed32 = input.ReadSFixed32();
+            break;
+          }
+          case 81: {
+            OptionalSfixed64 = input.ReadSFixed64();
+            break;
+          }
+          case 93: {
+            OptionalFloat = input.ReadFloat();
+            break;
+          }
+          case 97: {
+            OptionalDouble = input.ReadDouble();
+            break;
+          }
+          case 104: {
+            OptionalBool = input.ReadBool();
+            break;
+          }
+          case 114: {
+            OptionalString = input.ReadString();
+            break;
+          }
+          case 122: {
+            OptionalBytes = input.ReadBytes();
+            break;
+          }
+          case 146: {
+            if (optionalNestedMessage_ == null) {
+              OptionalNestedMessage = new global::ProtobufTestMessages.Proto2.TestAllTypesProto2.Types.NestedMessage();
+            }
+            input.ReadMessage(OptionalNestedMessage);
+            break;
+          }
+          case 154: {
+            if (optionalForeignMessage_ == null) {
+              OptionalForeignMessage = new global::ProtobufTestMessages.Proto2.ForeignMessageProto2();
+            }
+            input.ReadMessage(OptionalForeignMessage);
+            break;
+          }
+          case 168: {
+            OptionalNestedEnum = (global::ProtobufTestMessages.Proto2.TestAllTypesProto2.Types.NestedEnum) input.ReadEnum();
+            break;
+          }
+          case 176: {
+            OptionalForeignEnum = (global::ProtobufTestMessages.Proto2.ForeignEnumProto2) input.ReadEnum();
+            break;
+          }
+          case 194: {
+            OptionalStringPiece = input.ReadString();
+            break;
+          }
+          case 202: {
+            OptionalCord = input.ReadString();
+            break;
+          }
+          case 218: {
+            if (recursiveMessage_ == null) {
+              RecursiveMessage = new global::ProtobufTestMessages.Proto2.TestAllTypesProto2();
+            }
+            input.ReadMessage(RecursiveMessage);
+            break;
+          }
+          case 250:
+          case 248: {
+            repeatedInt32_.AddEntriesFrom(input, _repeated_repeatedInt32_codec);
+            break;
+          }
+          case 258:
+          case 256: {
+            repeatedInt64_.AddEntriesFrom(input, _repeated_repeatedInt64_codec);
+            break;
+          }
+          case 266:
+          case 264: {
+            repeatedUint32_.AddEntriesFrom(input, _repeated_repeatedUint32_codec);
+            break;
+          }
+          case 274:
+          case 272: {
+            repeatedUint64_.AddEntriesFrom(input, _repeated_repeatedUint64_codec);
+            break;
+          }
+          case 282:
+          case 280: {
+            repeatedSint32_.AddEntriesFrom(input, _repeated_repeatedSint32_codec);
+            break;
+          }
+          case 290:
+          case 288: {
+            repeatedSint64_.AddEntriesFrom(input, _repeated_repeatedSint64_codec);
+            break;
+          }
+          case 298:
+          case 301: {
+            repeatedFixed32_.AddEntriesFrom(input, _repeated_repeatedFixed32_codec);
+            break;
+          }
+          case 306:
+          case 305: {
+            repeatedFixed64_.AddEntriesFrom(input, _repeated_repeatedFixed64_codec);
+            break;
+          }
+          case 314:
+          case 317: {
+            repeatedSfixed32_.AddEntriesFrom(input, _repeated_repeatedSfixed32_codec);
+            break;
+          }
+          case 322:
+          case 321: {
+            repeatedSfixed64_.AddEntriesFrom(input, _repeated_repeatedSfixed64_codec);
+            break;
+          }
+          case 330:
+          case 333: {
+            repeatedFloat_.AddEntriesFrom(input, _repeated_repeatedFloat_codec);
+            break;
+          }
+          case 338:
+          case 337: {
+            repeatedDouble_.AddEntriesFrom(input, _repeated_repeatedDouble_codec);
+            break;
+          }
+          case 346:
+          case 344: {
+            repeatedBool_.AddEntriesFrom(input, _repeated_repeatedBool_codec);
+            break;
+          }
+          case 354: {
+            repeatedString_.AddEntriesFrom(input, _repeated_repeatedString_codec);
+            break;
+          }
+          case 362: {
+            repeatedBytes_.AddEntriesFrom(input, _repeated_repeatedBytes_codec);
+            break;
+          }
+          case 386: {
+            repeatedNestedMessage_.AddEntriesFrom(input, _repeated_repeatedNestedMessage_codec);
+            break;
+          }
+          case 394: {
+            repeatedForeignMessage_.AddEntriesFrom(input, _repeated_repeatedForeignMessage_codec);
+            break;
+          }
+          case 410:
+          case 408: {
+            repeatedNestedEnum_.AddEntriesFrom(input, _repeated_repeatedNestedEnum_codec);
+            break;
+          }
+          case 418:
+          case 416: {
+            repeatedForeignEnum_.AddEntriesFrom(input, _repeated_repeatedForeignEnum_codec);
+            break;
+          }
+          case 434: {
+            repeatedStringPiece_.AddEntriesFrom(input, _repeated_repeatedStringPiece_codec);
+            break;
+          }
+          case 442: {
+            repeatedCord_.AddEntriesFrom(input, _repeated_repeatedCord_codec);
+            break;
+          }
+          case 450: {
+            mapInt32Int32_.AddEntriesFrom(input, _map_mapInt32Int32_codec);
+            break;
+          }
+          case 458: {
+            mapInt64Int64_.AddEntriesFrom(input, _map_mapInt64Int64_codec);
+            break;
+          }
+          case 466: {
+            mapUint32Uint32_.AddEntriesFrom(input, _map_mapUint32Uint32_codec);
+            break;
+          }
+          case 474: {
+            mapUint64Uint64_.AddEntriesFrom(input, _map_mapUint64Uint64_codec);
+            break;
+          }
+          case 482: {
+            mapSint32Sint32_.AddEntriesFrom(input, _map_mapSint32Sint32_codec);
+            break;
+          }
+          case 490: {
+            mapSint64Sint64_.AddEntriesFrom(input, _map_mapSint64Sint64_codec);
+            break;
+          }
+          case 498: {
+            mapFixed32Fixed32_.AddEntriesFrom(input, _map_mapFixed32Fixed32_codec);
+            break;
+          }
+          case 506: {
+            mapFixed64Fixed64_.AddEntriesFrom(input, _map_mapFixed64Fixed64_codec);
+            break;
+          }
+          case 514: {
+            mapSfixed32Sfixed32_.AddEntriesFrom(input, _map_mapSfixed32Sfixed32_codec);
+            break;
+          }
+          case 522: {
+            mapSfixed64Sfixed64_.AddEntriesFrom(input, _map_mapSfixed64Sfixed64_codec);
+            break;
+          }
+          case 530: {
+            mapInt32Float_.AddEntriesFrom(input, _map_mapInt32Float_codec);
+            break;
+          }
+          case 538: {
+            mapInt32Double_.AddEntriesFrom(input, _map_mapInt32Double_codec);
+            break;
+          }
+          case 546: {
+            mapBoolBool_.AddEntriesFrom(input, _map_mapBoolBool_codec);
+            break;
+          }
+          case 554: {
+            mapStringString_.AddEntriesFrom(input, _map_mapStringString_codec);
+            break;
+          }
+          case 562: {
+            mapStringBytes_.AddEntriesFrom(input, _map_mapStringBytes_codec);
+            break;
+          }
+          case 570: {
+            mapStringNestedMessage_.AddEntriesFrom(input, _map_mapStringNestedMessage_codec);
+            break;
+          }
+          case 578: {
+            mapStringForeignMessage_.AddEntriesFrom(input, _map_mapStringForeignMessage_codec);
+            break;
+          }
+          case 586: {
+            mapStringNestedEnum_.AddEntriesFrom(input, _map_mapStringNestedEnum_codec);
+            break;
+          }
+          case 594: {
+            mapStringForeignEnum_.AddEntriesFrom(input, _map_mapStringForeignEnum_codec);
+            break;
+          }
+          case 602:
+          case 600: {
+            packedInt32_.AddEntriesFrom(input, _repeated_packedInt32_codec);
+            break;
+          }
+          case 610:
+          case 608: {
+            packedInt64_.AddEntriesFrom(input, _repeated_packedInt64_codec);
+            break;
+          }
+          case 618:
+          case 616: {
+            packedUint32_.AddEntriesFrom(input, _repeated_packedUint32_codec);
+            break;
+          }
+          case 626:
+          case 624: {
+            packedUint64_.AddEntriesFrom(input, _repeated_packedUint64_codec);
+            break;
+          }
+          case 634:
+          case 632: {
+            packedSint32_.AddEntriesFrom(input, _repeated_packedSint32_codec);
+            break;
+          }
+          case 642:
+          case 640: {
+            packedSint64_.AddEntriesFrom(input, _repeated_packedSint64_codec);
+            break;
+          }
+          case 650:
+          case 653: {
+            packedFixed32_.AddEntriesFrom(input, _repeated_packedFixed32_codec);
+            break;
+          }
+          case 658:
+          case 657: {
+            packedFixed64_.AddEntriesFrom(input, _repeated_packedFixed64_codec);
+            break;
+          }
+          case 666:
+          case 669: {
+            packedSfixed32_.AddEntriesFrom(input, _repeated_packedSfixed32_codec);
+            break;
+          }
+          case 674:
+          case 673: {
+            packedSfixed64_.AddEntriesFrom(input, _repeated_packedSfixed64_codec);
+            break;
+          }
+          case 682:
+          case 685: {
+            packedFloat_.AddEntriesFrom(input, _repeated_packedFloat_codec);
+            break;
+          }
+          case 690:
+          case 689: {
+            packedDouble_.AddEntriesFrom(input, _repeated_packedDouble_codec);
+            break;
+          }
+          case 698:
+          case 696: {
+            packedBool_.AddEntriesFrom(input, _repeated_packedBool_codec);
+            break;
+          }
+          case 706:
+          case 704: {
+            packedNestedEnum_.AddEntriesFrom(input, _repeated_packedNestedEnum_codec);
+            break;
+          }
+          case 714:
+          case 712: {
+            unpackedInt32_.AddEntriesFrom(input, _repeated_unpackedInt32_codec);
+            break;
+          }
+          case 722:
+          case 720: {
+            unpackedInt64_.AddEntriesFrom(input, _repeated_unpackedInt64_codec);
+            break;
+          }
+          case 730:
+          case 728: {
+            unpackedUint32_.AddEntriesFrom(input, _repeated_unpackedUint32_codec);
+            break;
+          }
+          case 738:
+          case 736: {
+            unpackedUint64_.AddEntriesFrom(input, _repeated_unpackedUint64_codec);
+            break;
+          }
+          case 746:
+          case 744: {
+            unpackedSint32_.AddEntriesFrom(input, _repeated_unpackedSint32_codec);
+            break;
+          }
+          case 754:
+          case 752: {
+            unpackedSint64_.AddEntriesFrom(input, _repeated_unpackedSint64_codec);
+            break;
+          }
+          case 762:
+          case 765: {
+            unpackedFixed32_.AddEntriesFrom(input, _repeated_unpackedFixed32_codec);
+            break;
+          }
+          case 770:
+          case 769: {
+            unpackedFixed64_.AddEntriesFrom(input, _repeated_unpackedFixed64_codec);
+            break;
+          }
+          case 778:
+          case 781: {
+            unpackedSfixed32_.AddEntriesFrom(input, _repeated_unpackedSfixed32_codec);
+            break;
+          }
+          case 786:
+          case 785: {
+            unpackedSfixed64_.AddEntriesFrom(input, _repeated_unpackedSfixed64_codec);
+            break;
+          }
+          case 794:
+          case 797: {
+            unpackedFloat_.AddEntriesFrom(input, _repeated_unpackedFloat_codec);
+            break;
+          }
+          case 802:
+          case 801: {
+            unpackedDouble_.AddEntriesFrom(input, _repeated_unpackedDouble_codec);
+            break;
+          }
+          case 810:
+          case 808: {
+            unpackedBool_.AddEntriesFrom(input, _repeated_unpackedBool_codec);
+            break;
+          }
+          case 818:
+          case 816: {
+            unpackedNestedEnum_.AddEntriesFrom(input, _repeated_unpackedNestedEnum_codec);
+            break;
+          }
+          case 888: {
+            OneofUint32 = input.ReadUInt32();
+            break;
+          }
+          case 898: {
+            global::ProtobufTestMessages.Proto2.TestAllTypesProto2.Types.NestedMessage subBuilder = new global::ProtobufTestMessages.Proto2.TestAllTypesProto2.Types.NestedMessage();
+            if (oneofFieldCase_ == OneofFieldOneofCase.OneofNestedMessage) {
+              subBuilder.MergeFrom(OneofNestedMessage);
+            }
+            input.ReadMessage(subBuilder);
+            OneofNestedMessage = subBuilder;
+            break;
+          }
+          case 906: {
+            OneofString = input.ReadString();
+            break;
+          }
+          case 914: {
+            OneofBytes = input.ReadBytes();
+            break;
+          }
+          case 920: {
+            OneofBool = input.ReadBool();
+            break;
+          }
+          case 928: {
+            OneofUint64 = input.ReadUInt64();
+            break;
+          }
+          case 941: {
+            OneofFloat = input.ReadFloat();
+            break;
+          }
+          case 945: {
+            OneofDouble = input.ReadDouble();
+            break;
+          }
+          case 952: {
+            oneofField_ = input.ReadEnum();
+            oneofFieldCase_ = OneofFieldOneofCase.OneofEnum;
+            break;
+          }
+          case 1611: {
+            if (!HasData) {
+              Data = new global::ProtobufTestMessages.Proto2.TestAllTypesProto2.Types.Data();
+            }
+            input.ReadGroup(Data);
+            break;
+          }
+          case 3208: {
+            Fieldname1 = input.ReadInt32();
+            break;
+          }
+          case 3216: {
+            FieldName2 = input.ReadInt32();
+            break;
+          }
+          case 3224: {
+            FieldName3 = input.ReadInt32();
+            break;
+          }
+          case 3232: {
+            FieldName4 = input.ReadInt32();
+            break;
+          }
+          case 3240: {
+            Field0Name5 = input.ReadInt32();
+            break;
+          }
+          case 3248: {
+            Field0Name6 = input.ReadInt32();
+            break;
+          }
+          case 3256: {
+            FieldName7 = input.ReadInt32();
+            break;
+          }
+          case 3264: {
+            FieldName8 = input.ReadInt32();
+            break;
+          }
+          case 3272: {
+            FieldName9 = input.ReadInt32();
+            break;
+          }
+          case 3280: {
+            FieldName10 = input.ReadInt32();
+            break;
+          }
+          case 3288: {
+            FIELDNAME11 = input.ReadInt32();
+            break;
+          }
+          case 3296: {
+            FIELDName12 = input.ReadInt32();
+            break;
+          }
+          case 3304: {
+            FieldName13 = input.ReadInt32();
+            break;
+          }
+          case 3312: {
+            FieldName14 = input.ReadInt32();
+            break;
+          }
+          case 3320: {
+            FieldName15 = input.ReadInt32();
+            break;
+          }
+          case 3328: {
+            FieldName16 = input.ReadInt32();
+            break;
+          }
+          case 3336: {
+            FieldName17 = input.ReadInt32();
+            break;
+          }
+          case 3344: {
+            FieldName18 = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -3860,6 +4411,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestAllTypesProto2, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -3897,7 +4449,11 @@
         [pbr::OriginalName("NEG")] Neg = -1,
       }
 
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -4052,9 +4608,32 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                A = input.ReadInt32();
+                break;
+              }
+              case 18: {
+                if (corecursive_ == null) {
+                  Corecursive = new global::ProtobufTestMessages.Proto2.TestAllTypesProto2();
+                }
+                input.ReadMessage(Corecursive);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -4077,13 +4656,18 @@
             }
           }
         }
+        #endif
 
       }
 
       /// <summary>
       /// groups
       /// </summary>
-      public sealed partial class Data : pb::IMessage<Data>, pb::IBufferMessage {
+      public sealed partial class Data : pb::IMessage<Data>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<Data> _parser = new pb::MessageParser<Data>(() => new Data());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -4248,9 +4832,31 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 1612:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 1616: {
+                GroupInt32 = input.ReadInt32();
+                break;
+              }
+              case 1624: {
+                GroupUint32 = input.ReadUInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -4272,13 +4878,18 @@
             }
           }
         }
+        #endif
 
       }
 
       /// <summary>
       /// message_set test case.
       /// </summary>
-      public sealed partial class MessageSetCorrect : pb::IExtendableMessage<MessageSetCorrect>, pb::IBufferMessage {
+      public sealed partial class MessageSetCorrect : pb::IExtendableMessage<MessageSetCorrect>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<MessageSetCorrect> _parser = new pb::MessageParser<MessageSetCorrect>(() => new MessageSetCorrect());
         private pb::UnknownFieldSet _unknownFields;
         private pb::ExtensionSet<MessageSetCorrect> _extensions;
@@ -4383,9 +4994,23 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+                  _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                }
+                break;
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -4399,6 +5024,7 @@
             }
           }
         }
+        #endif
 
         public TValue GetExtension<TValue>(pb::Extension<MessageSetCorrect, TValue> extension) {
           return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -4424,7 +5050,11 @@
 
       }
 
-      public sealed partial class MessageSetCorrectExtension1 : pb::IMessage<MessageSetCorrectExtension1>, pb::IBufferMessage {
+      public sealed partial class MessageSetCorrectExtension1 : pb::IMessage<MessageSetCorrectExtension1>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<MessageSetCorrectExtension1> _parser = new pb::MessageParser<MessageSetCorrectExtension1>(() => new MessageSetCorrectExtension1());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4549,9 +5179,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 202: {
+                Str = input.ReadString();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -4567,6 +5213,7 @@
             }
           }
         }
+        #endif
 
         #region Extensions
         /// <summary>Container for extensions for other messages declared in the MessageSetCorrectExtension1 message type.</summary>
@@ -4579,7 +5226,11 @@
 
       }
 
-      public sealed partial class MessageSetCorrectExtension2 : pb::IMessage<MessageSetCorrectExtension2>, pb::IBufferMessage {
+      public sealed partial class MessageSetCorrectExtension2 : pb::IMessage<MessageSetCorrectExtension2>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<MessageSetCorrectExtension2> _parser = new pb::MessageParser<MessageSetCorrectExtension2>(() => new MessageSetCorrectExtension2());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -4707,9 +5358,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 72: {
+                I = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -4725,6 +5392,7 @@
             }
           }
         }
+        #endif
 
         #region Extensions
         /// <summary>Container for extensions for other messages declared in the MessageSetCorrectExtension2 message type.</summary>
@@ -4742,7 +5410,11 @@
 
   }
 
-  public sealed partial class ForeignMessageProto2 : pb::IMessage<ForeignMessageProto2>, pb::IBufferMessage {
+  public sealed partial class ForeignMessageProto2 : pb::IMessage<ForeignMessageProto2>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ForeignMessageProto2> _parser = new pb::MessageParser<ForeignMessageProto2>(() => new ForeignMessageProto2());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -4870,9 +5542,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            C = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4888,10 +5576,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class UnknownToTestAllTypes : pb::IMessage<UnknownToTestAllTypes>, pb::IBufferMessage {
+  public sealed partial class UnknownToTestAllTypes : pb::IMessage<UnknownToTestAllTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<UnknownToTestAllTypes> _parser = new pb::MessageParser<UnknownToTestAllTypes>(() => new UnknownToTestAllTypes());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -5173,9 +5866,52 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8008: {
+            OptionalInt32 = input.ReadInt32();
+            break;
+          }
+          case 8018: {
+            OptionalString = input.ReadString();
+            break;
+          }
+          case 8026: {
+            if (nestedMessage_ == null) {
+              NestedMessage = new global::ProtobufTestMessages.Proto2.ForeignMessageProto2();
+            }
+            input.ReadMessage(NestedMessage);
+            break;
+          }
+          case 8035: {
+            if (!HasOptionalGroup) {
+              OptionalGroup = new global::ProtobufTestMessages.Proto2.UnknownToTestAllTypes.Types.OptionalGroup();
+            }
+            input.ReadGroup(OptionalGroup);
+            break;
+          }
+          case 8048: {
+            OptionalBool = input.ReadBool();
+            break;
+          }
+          case 8090:
+          case 8088: {
+            repeatedInt32_.AddEntriesFrom(input, _repeated_repeatedInt32_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5218,12 +5954,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the UnknownToTestAllTypes message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class OptionalGroup : pb::IMessage<OptionalGroup>, pb::IBufferMessage {
+      public sealed partial class OptionalGroup : pb::IMessage<OptionalGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<OptionalGroup> _parser = new pb::MessageParser<OptionalGroup>(() => new OptionalGroup());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -5351,9 +6092,27 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 8036:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                A = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -5371,6 +6130,7 @@
             }
           }
         }
+        #endif
 
       }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/TestMessagesProto3.cs b/csharp/src/Google.Protobuf.Test.TestProtos/TestMessagesProto3.cs
index 465d5e8..41bc006 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/TestMessagesProto3.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/TestMessagesProto3.cs
@@ -259,7 +259,11 @@
   /// could trigger bugs that occur in any message type in this file.  We verify
   /// this stays true in a unit test.
   /// </summary>
-  public sealed partial class TestAllTypesProto3 : pb::IMessage<TestAllTypesProto3>, pb::IBufferMessage {
+  public sealed partial class TestAllTypesProto3 : pb::IMessage<TestAllTypesProto3>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestAllTypesProto3> _parser = new pb::MessageParser<TestAllTypesProto3>(() => new TestAllTypesProto3());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3383,9 +3387,720 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            OptionalInt32 = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            OptionalInt64 = input.ReadInt64();
+            break;
+          }
+          case 24: {
+            OptionalUint32 = input.ReadUInt32();
+            break;
+          }
+          case 32: {
+            OptionalUint64 = input.ReadUInt64();
+            break;
+          }
+          case 40: {
+            OptionalSint32 = input.ReadSInt32();
+            break;
+          }
+          case 48: {
+            OptionalSint64 = input.ReadSInt64();
+            break;
+          }
+          case 61: {
+            OptionalFixed32 = input.ReadFixed32();
+            break;
+          }
+          case 65: {
+            OptionalFixed64 = input.ReadFixed64();
+            break;
+          }
+          case 77: {
+            OptionalSfixed32 = input.ReadSFixed32();
+            break;
+          }
+          case 81: {
+            OptionalSfixed64 = input.ReadSFixed64();
+            break;
+          }
+          case 93: {
+            OptionalFloat = input.ReadFloat();
+            break;
+          }
+          case 97: {
+            OptionalDouble = input.ReadDouble();
+            break;
+          }
+          case 104: {
+            OptionalBool = input.ReadBool();
+            break;
+          }
+          case 114: {
+            OptionalString = input.ReadString();
+            break;
+          }
+          case 122: {
+            OptionalBytes = input.ReadBytes();
+            break;
+          }
+          case 146: {
+            if (optionalNestedMessage_ == null) {
+              OptionalNestedMessage = new global::ProtobufTestMessages.Proto3.TestAllTypesProto3.Types.NestedMessage();
+            }
+            input.ReadMessage(OptionalNestedMessage);
+            break;
+          }
+          case 154: {
+            if (optionalForeignMessage_ == null) {
+              OptionalForeignMessage = new global::ProtobufTestMessages.Proto3.ForeignMessage();
+            }
+            input.ReadMessage(OptionalForeignMessage);
+            break;
+          }
+          case 168: {
+            OptionalNestedEnum = (global::ProtobufTestMessages.Proto3.TestAllTypesProto3.Types.NestedEnum) input.ReadEnum();
+            break;
+          }
+          case 176: {
+            OptionalForeignEnum = (global::ProtobufTestMessages.Proto3.ForeignEnum) input.ReadEnum();
+            break;
+          }
+          case 184: {
+            OptionalAliasedEnum = (global::ProtobufTestMessages.Proto3.TestAllTypesProto3.Types.AliasedEnum) input.ReadEnum();
+            break;
+          }
+          case 194: {
+            OptionalStringPiece = input.ReadString();
+            break;
+          }
+          case 202: {
+            OptionalCord = input.ReadString();
+            break;
+          }
+          case 218: {
+            if (recursiveMessage_ == null) {
+              RecursiveMessage = new global::ProtobufTestMessages.Proto3.TestAllTypesProto3();
+            }
+            input.ReadMessage(RecursiveMessage);
+            break;
+          }
+          case 250:
+          case 248: {
+            repeatedInt32_.AddEntriesFrom(input, _repeated_repeatedInt32_codec);
+            break;
+          }
+          case 258:
+          case 256: {
+            repeatedInt64_.AddEntriesFrom(input, _repeated_repeatedInt64_codec);
+            break;
+          }
+          case 266:
+          case 264: {
+            repeatedUint32_.AddEntriesFrom(input, _repeated_repeatedUint32_codec);
+            break;
+          }
+          case 274:
+          case 272: {
+            repeatedUint64_.AddEntriesFrom(input, _repeated_repeatedUint64_codec);
+            break;
+          }
+          case 282:
+          case 280: {
+            repeatedSint32_.AddEntriesFrom(input, _repeated_repeatedSint32_codec);
+            break;
+          }
+          case 290:
+          case 288: {
+            repeatedSint64_.AddEntriesFrom(input, _repeated_repeatedSint64_codec);
+            break;
+          }
+          case 298:
+          case 301: {
+            repeatedFixed32_.AddEntriesFrom(input, _repeated_repeatedFixed32_codec);
+            break;
+          }
+          case 306:
+          case 305: {
+            repeatedFixed64_.AddEntriesFrom(input, _repeated_repeatedFixed64_codec);
+            break;
+          }
+          case 314:
+          case 317: {
+            repeatedSfixed32_.AddEntriesFrom(input, _repeated_repeatedSfixed32_codec);
+            break;
+          }
+          case 322:
+          case 321: {
+            repeatedSfixed64_.AddEntriesFrom(input, _repeated_repeatedSfixed64_codec);
+            break;
+          }
+          case 330:
+          case 333: {
+            repeatedFloat_.AddEntriesFrom(input, _repeated_repeatedFloat_codec);
+            break;
+          }
+          case 338:
+          case 337: {
+            repeatedDouble_.AddEntriesFrom(input, _repeated_repeatedDouble_codec);
+            break;
+          }
+          case 346:
+          case 344: {
+            repeatedBool_.AddEntriesFrom(input, _repeated_repeatedBool_codec);
+            break;
+          }
+          case 354: {
+            repeatedString_.AddEntriesFrom(input, _repeated_repeatedString_codec);
+            break;
+          }
+          case 362: {
+            repeatedBytes_.AddEntriesFrom(input, _repeated_repeatedBytes_codec);
+            break;
+          }
+          case 386: {
+            repeatedNestedMessage_.AddEntriesFrom(input, _repeated_repeatedNestedMessage_codec);
+            break;
+          }
+          case 394: {
+            repeatedForeignMessage_.AddEntriesFrom(input, _repeated_repeatedForeignMessage_codec);
+            break;
+          }
+          case 410:
+          case 408: {
+            repeatedNestedEnum_.AddEntriesFrom(input, _repeated_repeatedNestedEnum_codec);
+            break;
+          }
+          case 418:
+          case 416: {
+            repeatedForeignEnum_.AddEntriesFrom(input, _repeated_repeatedForeignEnum_codec);
+            break;
+          }
+          case 434: {
+            repeatedStringPiece_.AddEntriesFrom(input, _repeated_repeatedStringPiece_codec);
+            break;
+          }
+          case 442: {
+            repeatedCord_.AddEntriesFrom(input, _repeated_repeatedCord_codec);
+            break;
+          }
+          case 450: {
+            mapInt32Int32_.AddEntriesFrom(input, _map_mapInt32Int32_codec);
+            break;
+          }
+          case 458: {
+            mapInt64Int64_.AddEntriesFrom(input, _map_mapInt64Int64_codec);
+            break;
+          }
+          case 466: {
+            mapUint32Uint32_.AddEntriesFrom(input, _map_mapUint32Uint32_codec);
+            break;
+          }
+          case 474: {
+            mapUint64Uint64_.AddEntriesFrom(input, _map_mapUint64Uint64_codec);
+            break;
+          }
+          case 482: {
+            mapSint32Sint32_.AddEntriesFrom(input, _map_mapSint32Sint32_codec);
+            break;
+          }
+          case 490: {
+            mapSint64Sint64_.AddEntriesFrom(input, _map_mapSint64Sint64_codec);
+            break;
+          }
+          case 498: {
+            mapFixed32Fixed32_.AddEntriesFrom(input, _map_mapFixed32Fixed32_codec);
+            break;
+          }
+          case 506: {
+            mapFixed64Fixed64_.AddEntriesFrom(input, _map_mapFixed64Fixed64_codec);
+            break;
+          }
+          case 514: {
+            mapSfixed32Sfixed32_.AddEntriesFrom(input, _map_mapSfixed32Sfixed32_codec);
+            break;
+          }
+          case 522: {
+            mapSfixed64Sfixed64_.AddEntriesFrom(input, _map_mapSfixed64Sfixed64_codec);
+            break;
+          }
+          case 530: {
+            mapInt32Float_.AddEntriesFrom(input, _map_mapInt32Float_codec);
+            break;
+          }
+          case 538: {
+            mapInt32Double_.AddEntriesFrom(input, _map_mapInt32Double_codec);
+            break;
+          }
+          case 546: {
+            mapBoolBool_.AddEntriesFrom(input, _map_mapBoolBool_codec);
+            break;
+          }
+          case 554: {
+            mapStringString_.AddEntriesFrom(input, _map_mapStringString_codec);
+            break;
+          }
+          case 562: {
+            mapStringBytes_.AddEntriesFrom(input, _map_mapStringBytes_codec);
+            break;
+          }
+          case 570: {
+            mapStringNestedMessage_.AddEntriesFrom(input, _map_mapStringNestedMessage_codec);
+            break;
+          }
+          case 578: {
+            mapStringForeignMessage_.AddEntriesFrom(input, _map_mapStringForeignMessage_codec);
+            break;
+          }
+          case 586: {
+            mapStringNestedEnum_.AddEntriesFrom(input, _map_mapStringNestedEnum_codec);
+            break;
+          }
+          case 594: {
+            mapStringForeignEnum_.AddEntriesFrom(input, _map_mapStringForeignEnum_codec);
+            break;
+          }
+          case 602:
+          case 600: {
+            packedInt32_.AddEntriesFrom(input, _repeated_packedInt32_codec);
+            break;
+          }
+          case 610:
+          case 608: {
+            packedInt64_.AddEntriesFrom(input, _repeated_packedInt64_codec);
+            break;
+          }
+          case 618:
+          case 616: {
+            packedUint32_.AddEntriesFrom(input, _repeated_packedUint32_codec);
+            break;
+          }
+          case 626:
+          case 624: {
+            packedUint64_.AddEntriesFrom(input, _repeated_packedUint64_codec);
+            break;
+          }
+          case 634:
+          case 632: {
+            packedSint32_.AddEntriesFrom(input, _repeated_packedSint32_codec);
+            break;
+          }
+          case 642:
+          case 640: {
+            packedSint64_.AddEntriesFrom(input, _repeated_packedSint64_codec);
+            break;
+          }
+          case 650:
+          case 653: {
+            packedFixed32_.AddEntriesFrom(input, _repeated_packedFixed32_codec);
+            break;
+          }
+          case 658:
+          case 657: {
+            packedFixed64_.AddEntriesFrom(input, _repeated_packedFixed64_codec);
+            break;
+          }
+          case 666:
+          case 669: {
+            packedSfixed32_.AddEntriesFrom(input, _repeated_packedSfixed32_codec);
+            break;
+          }
+          case 674:
+          case 673: {
+            packedSfixed64_.AddEntriesFrom(input, _repeated_packedSfixed64_codec);
+            break;
+          }
+          case 682:
+          case 685: {
+            packedFloat_.AddEntriesFrom(input, _repeated_packedFloat_codec);
+            break;
+          }
+          case 690:
+          case 689: {
+            packedDouble_.AddEntriesFrom(input, _repeated_packedDouble_codec);
+            break;
+          }
+          case 698:
+          case 696: {
+            packedBool_.AddEntriesFrom(input, _repeated_packedBool_codec);
+            break;
+          }
+          case 706:
+          case 704: {
+            packedNestedEnum_.AddEntriesFrom(input, _repeated_packedNestedEnum_codec);
+            break;
+          }
+          case 714:
+          case 712: {
+            unpackedInt32_.AddEntriesFrom(input, _repeated_unpackedInt32_codec);
+            break;
+          }
+          case 722:
+          case 720: {
+            unpackedInt64_.AddEntriesFrom(input, _repeated_unpackedInt64_codec);
+            break;
+          }
+          case 730:
+          case 728: {
+            unpackedUint32_.AddEntriesFrom(input, _repeated_unpackedUint32_codec);
+            break;
+          }
+          case 738:
+          case 736: {
+            unpackedUint64_.AddEntriesFrom(input, _repeated_unpackedUint64_codec);
+            break;
+          }
+          case 746:
+          case 744: {
+            unpackedSint32_.AddEntriesFrom(input, _repeated_unpackedSint32_codec);
+            break;
+          }
+          case 754:
+          case 752: {
+            unpackedSint64_.AddEntriesFrom(input, _repeated_unpackedSint64_codec);
+            break;
+          }
+          case 762:
+          case 765: {
+            unpackedFixed32_.AddEntriesFrom(input, _repeated_unpackedFixed32_codec);
+            break;
+          }
+          case 770:
+          case 769: {
+            unpackedFixed64_.AddEntriesFrom(input, _repeated_unpackedFixed64_codec);
+            break;
+          }
+          case 778:
+          case 781: {
+            unpackedSfixed32_.AddEntriesFrom(input, _repeated_unpackedSfixed32_codec);
+            break;
+          }
+          case 786:
+          case 785: {
+            unpackedSfixed64_.AddEntriesFrom(input, _repeated_unpackedSfixed64_codec);
+            break;
+          }
+          case 794:
+          case 797: {
+            unpackedFloat_.AddEntriesFrom(input, _repeated_unpackedFloat_codec);
+            break;
+          }
+          case 802:
+          case 801: {
+            unpackedDouble_.AddEntriesFrom(input, _repeated_unpackedDouble_codec);
+            break;
+          }
+          case 810:
+          case 808: {
+            unpackedBool_.AddEntriesFrom(input, _repeated_unpackedBool_codec);
+            break;
+          }
+          case 818:
+          case 816: {
+            unpackedNestedEnum_.AddEntriesFrom(input, _repeated_unpackedNestedEnum_codec);
+            break;
+          }
+          case 888: {
+            OneofUint32 = input.ReadUInt32();
+            break;
+          }
+          case 898: {
+            global::ProtobufTestMessages.Proto3.TestAllTypesProto3.Types.NestedMessage subBuilder = new global::ProtobufTestMessages.Proto3.TestAllTypesProto3.Types.NestedMessage();
+            if (oneofFieldCase_ == OneofFieldOneofCase.OneofNestedMessage) {
+              subBuilder.MergeFrom(OneofNestedMessage);
+            }
+            input.ReadMessage(subBuilder);
+            OneofNestedMessage = subBuilder;
+            break;
+          }
+          case 906: {
+            OneofString = input.ReadString();
+            break;
+          }
+          case 914: {
+            OneofBytes = input.ReadBytes();
+            break;
+          }
+          case 920: {
+            OneofBool = input.ReadBool();
+            break;
+          }
+          case 928: {
+            OneofUint64 = input.ReadUInt64();
+            break;
+          }
+          case 941: {
+            OneofFloat = input.ReadFloat();
+            break;
+          }
+          case 945: {
+            OneofDouble = input.ReadDouble();
+            break;
+          }
+          case 952: {
+            oneofField_ = input.ReadEnum();
+            oneofFieldCase_ = OneofFieldOneofCase.OneofEnum;
+            break;
+          }
+          case 1610: {
+            bool? value = _single_optionalBoolWrapper_codec.Read(input);
+            if (optionalBoolWrapper_ == null || value != false) {
+              OptionalBoolWrapper = value;
+            }
+            break;
+          }
+          case 1618: {
+            int? value = _single_optionalInt32Wrapper_codec.Read(input);
+            if (optionalInt32Wrapper_ == null || value != 0) {
+              OptionalInt32Wrapper = value;
+            }
+            break;
+          }
+          case 1626: {
+            long? value = _single_optionalInt64Wrapper_codec.Read(input);
+            if (optionalInt64Wrapper_ == null || value != 0L) {
+              OptionalInt64Wrapper = value;
+            }
+            break;
+          }
+          case 1634: {
+            uint? value = _single_optionalUint32Wrapper_codec.Read(input);
+            if (optionalUint32Wrapper_ == null || value != 0) {
+              OptionalUint32Wrapper = value;
+            }
+            break;
+          }
+          case 1642: {
+            ulong? value = _single_optionalUint64Wrapper_codec.Read(input);
+            if (optionalUint64Wrapper_ == null || value != 0UL) {
+              OptionalUint64Wrapper = value;
+            }
+            break;
+          }
+          case 1650: {
+            float? value = _single_optionalFloatWrapper_codec.Read(input);
+            if (optionalFloatWrapper_ == null || value != 0F) {
+              OptionalFloatWrapper = value;
+            }
+            break;
+          }
+          case 1658: {
+            double? value = _single_optionalDoubleWrapper_codec.Read(input);
+            if (optionalDoubleWrapper_ == null || value != 0D) {
+              OptionalDoubleWrapper = value;
+            }
+            break;
+          }
+          case 1666: {
+            string value = _single_optionalStringWrapper_codec.Read(input);
+            if (optionalStringWrapper_ == null || value != "") {
+              OptionalStringWrapper = value;
+            }
+            break;
+          }
+          case 1674: {
+            pb::ByteString value = _single_optionalBytesWrapper_codec.Read(input);
+            if (optionalBytesWrapper_ == null || value != pb::ByteString.Empty) {
+              OptionalBytesWrapper = value;
+            }
+            break;
+          }
+          case 1690: {
+            repeatedBoolWrapper_.AddEntriesFrom(input, _repeated_repeatedBoolWrapper_codec);
+            break;
+          }
+          case 1698: {
+            repeatedInt32Wrapper_.AddEntriesFrom(input, _repeated_repeatedInt32Wrapper_codec);
+            break;
+          }
+          case 1706: {
+            repeatedInt64Wrapper_.AddEntriesFrom(input, _repeated_repeatedInt64Wrapper_codec);
+            break;
+          }
+          case 1714: {
+            repeatedUint32Wrapper_.AddEntriesFrom(input, _repeated_repeatedUint32Wrapper_codec);
+            break;
+          }
+          case 1722: {
+            repeatedUint64Wrapper_.AddEntriesFrom(input, _repeated_repeatedUint64Wrapper_codec);
+            break;
+          }
+          case 1730: {
+            repeatedFloatWrapper_.AddEntriesFrom(input, _repeated_repeatedFloatWrapper_codec);
+            break;
+          }
+          case 1738: {
+            repeatedDoubleWrapper_.AddEntriesFrom(input, _repeated_repeatedDoubleWrapper_codec);
+            break;
+          }
+          case 1746: {
+            repeatedStringWrapper_.AddEntriesFrom(input, _repeated_repeatedStringWrapper_codec);
+            break;
+          }
+          case 1754: {
+            repeatedBytesWrapper_.AddEntriesFrom(input, _repeated_repeatedBytesWrapper_codec);
+            break;
+          }
+          case 2410: {
+            if (optionalDuration_ == null) {
+              OptionalDuration = new global::Google.Protobuf.WellKnownTypes.Duration();
+            }
+            input.ReadMessage(OptionalDuration);
+            break;
+          }
+          case 2418: {
+            if (optionalTimestamp_ == null) {
+              OptionalTimestamp = new global::Google.Protobuf.WellKnownTypes.Timestamp();
+            }
+            input.ReadMessage(OptionalTimestamp);
+            break;
+          }
+          case 2426: {
+            if (optionalFieldMask_ == null) {
+              OptionalFieldMask = new global::Google.Protobuf.WellKnownTypes.FieldMask();
+            }
+            input.ReadMessage(OptionalFieldMask);
+            break;
+          }
+          case 2434: {
+            if (optionalStruct_ == null) {
+              OptionalStruct = new global::Google.Protobuf.WellKnownTypes.Struct();
+            }
+            input.ReadMessage(OptionalStruct);
+            break;
+          }
+          case 2442: {
+            if (optionalAny_ == null) {
+              OptionalAny = new global::Google.Protobuf.WellKnownTypes.Any();
+            }
+            input.ReadMessage(OptionalAny);
+            break;
+          }
+          case 2450: {
+            if (optionalValue_ == null) {
+              OptionalValue = new global::Google.Protobuf.WellKnownTypes.Value();
+            }
+            input.ReadMessage(OptionalValue);
+            break;
+          }
+          case 2490: {
+            repeatedDuration_.AddEntriesFrom(input, _repeated_repeatedDuration_codec);
+            break;
+          }
+          case 2498: {
+            repeatedTimestamp_.AddEntriesFrom(input, _repeated_repeatedTimestamp_codec);
+            break;
+          }
+          case 2506: {
+            repeatedFieldmask_.AddEntriesFrom(input, _repeated_repeatedFieldmask_codec);
+            break;
+          }
+          case 2522: {
+            repeatedAny_.AddEntriesFrom(input, _repeated_repeatedAny_codec);
+            break;
+          }
+          case 2530: {
+            repeatedValue_.AddEntriesFrom(input, _repeated_repeatedValue_codec);
+            break;
+          }
+          case 2538: {
+            repeatedListValue_.AddEntriesFrom(input, _repeated_repeatedListValue_codec);
+            break;
+          }
+          case 2594: {
+            repeatedStruct_.AddEntriesFrom(input, _repeated_repeatedStruct_codec);
+            break;
+          }
+          case 3208: {
+            Fieldname1 = input.ReadInt32();
+            break;
+          }
+          case 3216: {
+            FieldName2 = input.ReadInt32();
+            break;
+          }
+          case 3224: {
+            FieldName3 = input.ReadInt32();
+            break;
+          }
+          case 3232: {
+            FieldName4 = input.ReadInt32();
+            break;
+          }
+          case 3240: {
+            Field0Name5 = input.ReadInt32();
+            break;
+          }
+          case 3248: {
+            Field0Name6 = input.ReadInt32();
+            break;
+          }
+          case 3256: {
+            FieldName7 = input.ReadInt32();
+            break;
+          }
+          case 3264: {
+            FieldName8 = input.ReadInt32();
+            break;
+          }
+          case 3272: {
+            FieldName9 = input.ReadInt32();
+            break;
+          }
+          case 3280: {
+            FieldName10 = input.ReadInt32();
+            break;
+          }
+          case 3288: {
+            FIELDNAME11 = input.ReadInt32();
+            break;
+          }
+          case 3296: {
+            FIELDName12 = input.ReadInt32();
+            break;
+          }
+          case 3304: {
+            FieldName13 = input.ReadInt32();
+            break;
+          }
+          case 3312: {
+            FieldName14 = input.ReadInt32();
+            break;
+          }
+          case 3320: {
+            FieldName15 = input.ReadInt32();
+            break;
+          }
+          case 3328: {
+            FieldName16 = input.ReadInt32();
+            break;
+          }
+          case 3336: {
+            FieldName17 = input.ReadInt32();
+            break;
+          }
+          case 3344: {
+            FieldName18 = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4096,6 +4811,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestAllTypesProto3 message type.</summary>
@@ -4120,7 +4836,11 @@
         [pbr::OriginalName("bAz", PreferredAlias = false)] BAz = 2,
       }
 
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4260,9 +4980,32 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                A = input.ReadInt32();
+                break;
+              }
+              case 18: {
+                if (corecursive_ == null) {
+                  Corecursive = new global::ProtobufTestMessages.Proto3.TestAllTypesProto3();
+                }
+                input.ReadMessage(Corecursive);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -4285,6 +5028,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -4293,7 +5037,11 @@
 
   }
 
-  public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage>, pb::IBufferMessage {
+  public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ForeignMessage> _parser = new pb::MessageParser<ForeignMessage>(() => new ForeignMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4406,9 +5154,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            C = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4424,6 +5188,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/Unittest.cs b/csharp/src/Google.Protobuf.Test.TestProtos/Unittest.cs
index 9b5825a..373f569 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/Unittest.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/Unittest.cs
@@ -1120,7 +1120,11 @@
   /// This proto includes every type of field in both singular and repeated
   /// forms.
   /// </summary>
-  public sealed partial class TestAllTypes : pb::IMessage<TestAllTypes>, pb::IBufferMessage {
+  public sealed partial class TestAllTypes : pb::IMessage<TestAllTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestAllTypes> _parser = new pb::MessageParser<TestAllTypes>(() => new TestAllTypes());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -3442,9 +3446,360 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            OptionalInt32 = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            OptionalInt64 = input.ReadInt64();
+            break;
+          }
+          case 24: {
+            OptionalUint32 = input.ReadUInt32();
+            break;
+          }
+          case 32: {
+            OptionalUint64 = input.ReadUInt64();
+            break;
+          }
+          case 40: {
+            OptionalSint32 = input.ReadSInt32();
+            break;
+          }
+          case 48: {
+            OptionalSint64 = input.ReadSInt64();
+            break;
+          }
+          case 61: {
+            OptionalFixed32 = input.ReadFixed32();
+            break;
+          }
+          case 65: {
+            OptionalFixed64 = input.ReadFixed64();
+            break;
+          }
+          case 77: {
+            OptionalSfixed32 = input.ReadSFixed32();
+            break;
+          }
+          case 81: {
+            OptionalSfixed64 = input.ReadSFixed64();
+            break;
+          }
+          case 93: {
+            OptionalFloat = input.ReadFloat();
+            break;
+          }
+          case 97: {
+            OptionalDouble = input.ReadDouble();
+            break;
+          }
+          case 104: {
+            OptionalBool = input.ReadBool();
+            break;
+          }
+          case 114: {
+            OptionalString = input.ReadString();
+            break;
+          }
+          case 122: {
+            OptionalBytes = input.ReadBytes();
+            break;
+          }
+          case 131: {
+            if (!HasOptionalGroup) {
+              OptionalGroup = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes.Types.OptionalGroup();
+            }
+            input.ReadGroup(OptionalGroup);
+            break;
+          }
+          case 146: {
+            if (optionalNestedMessage_ == null) {
+              OptionalNestedMessage = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes.Types.NestedMessage();
+            }
+            input.ReadMessage(OptionalNestedMessage);
+            break;
+          }
+          case 154: {
+            if (optionalForeignMessage_ == null) {
+              OptionalForeignMessage = new global::Google.Protobuf.TestProtos.Proto2.ForeignMessage();
+            }
+            input.ReadMessage(OptionalForeignMessage);
+            break;
+          }
+          case 162: {
+            if (optionalImportMessage_ == null) {
+              OptionalImportMessage = new global::Google.Protobuf.TestProtos.Proto2.ImportMessage();
+            }
+            input.ReadMessage(OptionalImportMessage);
+            break;
+          }
+          case 168: {
+            OptionalNestedEnum = (global::Google.Protobuf.TestProtos.Proto2.TestAllTypes.Types.NestedEnum) input.ReadEnum();
+            break;
+          }
+          case 176: {
+            OptionalForeignEnum = (global::Google.Protobuf.TestProtos.Proto2.ForeignEnum) input.ReadEnum();
+            break;
+          }
+          case 184: {
+            OptionalImportEnum = (global::Google.Protobuf.TestProtos.Proto2.ImportEnum) input.ReadEnum();
+            break;
+          }
+          case 194: {
+            OptionalStringPiece = input.ReadString();
+            break;
+          }
+          case 202: {
+            OptionalCord = input.ReadString();
+            break;
+          }
+          case 210: {
+            if (optionalPublicImportMessage_ == null) {
+              OptionalPublicImportMessage = new global::Google.Protobuf.TestProtos.Proto2.PublicImportMessage();
+            }
+            input.ReadMessage(OptionalPublicImportMessage);
+            break;
+          }
+          case 218: {
+            if (optionalLazyMessage_ == null) {
+              OptionalLazyMessage = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes.Types.NestedMessage();
+            }
+            input.ReadMessage(OptionalLazyMessage);
+            break;
+          }
+          case 250:
+          case 248: {
+            repeatedInt32_.AddEntriesFrom(input, _repeated_repeatedInt32_codec);
+            break;
+          }
+          case 258:
+          case 256: {
+            repeatedInt64_.AddEntriesFrom(input, _repeated_repeatedInt64_codec);
+            break;
+          }
+          case 266:
+          case 264: {
+            repeatedUint32_.AddEntriesFrom(input, _repeated_repeatedUint32_codec);
+            break;
+          }
+          case 274:
+          case 272: {
+            repeatedUint64_.AddEntriesFrom(input, _repeated_repeatedUint64_codec);
+            break;
+          }
+          case 282:
+          case 280: {
+            repeatedSint32_.AddEntriesFrom(input, _repeated_repeatedSint32_codec);
+            break;
+          }
+          case 290:
+          case 288: {
+            repeatedSint64_.AddEntriesFrom(input, _repeated_repeatedSint64_codec);
+            break;
+          }
+          case 298:
+          case 301: {
+            repeatedFixed32_.AddEntriesFrom(input, _repeated_repeatedFixed32_codec);
+            break;
+          }
+          case 306:
+          case 305: {
+            repeatedFixed64_.AddEntriesFrom(input, _repeated_repeatedFixed64_codec);
+            break;
+          }
+          case 314:
+          case 317: {
+            repeatedSfixed32_.AddEntriesFrom(input, _repeated_repeatedSfixed32_codec);
+            break;
+          }
+          case 322:
+          case 321: {
+            repeatedSfixed64_.AddEntriesFrom(input, _repeated_repeatedSfixed64_codec);
+            break;
+          }
+          case 330:
+          case 333: {
+            repeatedFloat_.AddEntriesFrom(input, _repeated_repeatedFloat_codec);
+            break;
+          }
+          case 338:
+          case 337: {
+            repeatedDouble_.AddEntriesFrom(input, _repeated_repeatedDouble_codec);
+            break;
+          }
+          case 346:
+          case 344: {
+            repeatedBool_.AddEntriesFrom(input, _repeated_repeatedBool_codec);
+            break;
+          }
+          case 354: {
+            repeatedString_.AddEntriesFrom(input, _repeated_repeatedString_codec);
+            break;
+          }
+          case 362: {
+            repeatedBytes_.AddEntriesFrom(input, _repeated_repeatedBytes_codec);
+            break;
+          }
+          case 371: {
+            repeatedGroup_.AddEntriesFrom(input, _repeated_repeatedGroup_codec);
+            break;
+          }
+          case 386: {
+            repeatedNestedMessage_.AddEntriesFrom(input, _repeated_repeatedNestedMessage_codec);
+            break;
+          }
+          case 394: {
+            repeatedForeignMessage_.AddEntriesFrom(input, _repeated_repeatedForeignMessage_codec);
+            break;
+          }
+          case 402: {
+            repeatedImportMessage_.AddEntriesFrom(input, _repeated_repeatedImportMessage_codec);
+            break;
+          }
+          case 410:
+          case 408: {
+            repeatedNestedEnum_.AddEntriesFrom(input, _repeated_repeatedNestedEnum_codec);
+            break;
+          }
+          case 418:
+          case 416: {
+            repeatedForeignEnum_.AddEntriesFrom(input, _repeated_repeatedForeignEnum_codec);
+            break;
+          }
+          case 426:
+          case 424: {
+            repeatedImportEnum_.AddEntriesFrom(input, _repeated_repeatedImportEnum_codec);
+            break;
+          }
+          case 434: {
+            repeatedStringPiece_.AddEntriesFrom(input, _repeated_repeatedStringPiece_codec);
+            break;
+          }
+          case 442: {
+            repeatedCord_.AddEntriesFrom(input, _repeated_repeatedCord_codec);
+            break;
+          }
+          case 458: {
+            repeatedLazyMessage_.AddEntriesFrom(input, _repeated_repeatedLazyMessage_codec);
+            break;
+          }
+          case 488: {
+            DefaultInt32 = input.ReadInt32();
+            break;
+          }
+          case 496: {
+            DefaultInt64 = input.ReadInt64();
+            break;
+          }
+          case 504: {
+            DefaultUint32 = input.ReadUInt32();
+            break;
+          }
+          case 512: {
+            DefaultUint64 = input.ReadUInt64();
+            break;
+          }
+          case 520: {
+            DefaultSint32 = input.ReadSInt32();
+            break;
+          }
+          case 528: {
+            DefaultSint64 = input.ReadSInt64();
+            break;
+          }
+          case 541: {
+            DefaultFixed32 = input.ReadFixed32();
+            break;
+          }
+          case 545: {
+            DefaultFixed64 = input.ReadFixed64();
+            break;
+          }
+          case 557: {
+            DefaultSfixed32 = input.ReadSFixed32();
+            break;
+          }
+          case 561: {
+            DefaultSfixed64 = input.ReadSFixed64();
+            break;
+          }
+          case 573: {
+            DefaultFloat = input.ReadFloat();
+            break;
+          }
+          case 577: {
+            DefaultDouble = input.ReadDouble();
+            break;
+          }
+          case 584: {
+            DefaultBool = input.ReadBool();
+            break;
+          }
+          case 594: {
+            DefaultString = input.ReadString();
+            break;
+          }
+          case 602: {
+            DefaultBytes = input.ReadBytes();
+            break;
+          }
+          case 648: {
+            DefaultNestedEnum = (global::Google.Protobuf.TestProtos.Proto2.TestAllTypes.Types.NestedEnum) input.ReadEnum();
+            break;
+          }
+          case 656: {
+            DefaultForeignEnum = (global::Google.Protobuf.TestProtos.Proto2.ForeignEnum) input.ReadEnum();
+            break;
+          }
+          case 664: {
+            DefaultImportEnum = (global::Google.Protobuf.TestProtos.Proto2.ImportEnum) input.ReadEnum();
+            break;
+          }
+          case 674: {
+            DefaultStringPiece = input.ReadString();
+            break;
+          }
+          case 682: {
+            DefaultCord = input.ReadString();
+            break;
+          }
+          case 888: {
+            OneofUint32 = input.ReadUInt32();
+            break;
+          }
+          case 898: {
+            global::Google.Protobuf.TestProtos.Proto2.TestAllTypes.Types.NestedMessage subBuilder = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes.Types.NestedMessage();
+            if (oneofFieldCase_ == OneofFieldOneofCase.OneofNestedMessage) {
+              subBuilder.MergeFrom(OneofNestedMessage);
+            }
+            input.ReadMessage(subBuilder);
+            OneofNestedMessage = subBuilder;
+            break;
+          }
+          case 906: {
+            OneofString = input.ReadString();
+            break;
+          }
+          case 914: {
+            OneofBytes = input.ReadBytes();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -3795,6 +4150,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestAllTypes message type.</summary>
@@ -3810,7 +4166,11 @@
         [pbr::OriginalName("NEG")] Neg = -1,
       }
 
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -3943,9 +4303,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                Bb = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -3961,10 +4337,15 @@
             }
           }
         }
+        #endif
 
       }
 
-      public sealed partial class OptionalGroup : pb::IMessage<OptionalGroup>, pb::IBufferMessage {
+      public sealed partial class OptionalGroup : pb::IMessage<OptionalGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<OptionalGroup> _parser = new pb::MessageParser<OptionalGroup>(() => new OptionalGroup());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -4092,9 +4473,27 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 132:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 136: {
+                A = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -4112,10 +4511,15 @@
             }
           }
         }
+        #endif
 
       }
 
-      public sealed partial class RepeatedGroup : pb::IMessage<RepeatedGroup>, pb::IBufferMessage {
+      public sealed partial class RepeatedGroup : pb::IMessage<RepeatedGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<RepeatedGroup> _parser = new pb::MessageParser<RepeatedGroup>(() => new RepeatedGroup());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -4243,9 +4647,27 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 372:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 376: {
+                A = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -4263,6 +4685,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -4274,7 +4697,11 @@
   /// <summary>
   /// This proto includes a recursively nested message.
   /// </summary>
-  public sealed partial class NestedTestAllTypes : pb::IMessage<NestedTestAllTypes>, pb::IBufferMessage {
+  public sealed partial class NestedTestAllTypes : pb::IMessage<NestedTestAllTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<NestedTestAllTypes> _parser = new pb::MessageParser<NestedTestAllTypes>(() => new NestedTestAllTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4433,9 +4860,39 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (child_ == null) {
+              Child = new global::Google.Protobuf.TestProtos.Proto2.NestedTestAllTypes();
+            }
+            input.ReadMessage(Child);
+            break;
+          }
+          case 18: {
+            if (payload_ == null) {
+              Payload = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+            }
+            input.ReadMessage(Payload);
+            break;
+          }
+          case 26: {
+            repeatedChild_.AddEntriesFrom(input, _repeated_repeatedChild_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4465,10 +4922,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestDeprecatedFields : pb::IMessage<TestDeprecatedFields>, pb::IBufferMessage {
+  public sealed partial class TestDeprecatedFields : pb::IMessage<TestDeprecatedFields>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestDeprecatedFields> _parser = new pb::MessageParser<TestDeprecatedFields>(() => new TestDeprecatedFields());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -4666,9 +5128,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            DeprecatedInt32 = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            DeprecatedInt32InOneof = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4688,11 +5170,16 @@
         }
       }
     }
+    #endif
 
   }
 
   [global::System.ObsoleteAttribute]
-  public sealed partial class TestDeprecatedMessage : pb::IMessage<TestDeprecatedMessage>, pb::IBufferMessage {
+  public sealed partial class TestDeprecatedMessage : pb::IMessage<TestDeprecatedMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestDeprecatedMessage> _parser = new pb::MessageParser<TestDeprecatedMessage>(() => new TestDeprecatedMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4781,9 +5268,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4795,6 +5294,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -4802,7 +5302,11 @@
   /// Define these after TestAllTypes to make sure the compiler can handle
   /// that.
   /// </summary>
-  public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage>, pb::IBufferMessage {
+  public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ForeignMessage> _parser = new pb::MessageParser<ForeignMessage>(() => new ForeignMessage());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -4967,9 +5471,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            C = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            D = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4989,10 +5513,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestReservedFields : pb::IMessage<TestReservedFields>, pb::IBufferMessage {
+  public sealed partial class TestReservedFields : pb::IMessage<TestReservedFields>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestReservedFields> _parser = new pb::MessageParser<TestReservedFields>(() => new TestReservedFields());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5081,9 +5610,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5095,10 +5636,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestAllExtensions : pb::IExtendableMessage<TestAllExtensions>, pb::IBufferMessage {
+  public sealed partial class TestAllExtensions : pb::IExtendableMessage<TestAllExtensions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestAllExtensions> _parser = new pb::MessageParser<TestAllExtensions>(() => new TestAllExtensions());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestAllExtensions> _extensions;
@@ -5203,9 +5749,23 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5219,6 +5779,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestAllExtensions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -5244,7 +5805,11 @@
 
   }
 
-  public sealed partial class OptionalGroup_extension : pb::IMessage<OptionalGroup_extension>, pb::IBufferMessage {
+  public sealed partial class OptionalGroup_extension : pb::IMessage<OptionalGroup_extension>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<OptionalGroup_extension> _parser = new pb::MessageParser<OptionalGroup_extension>(() => new OptionalGroup_extension());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -5372,9 +5937,27 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          case 132:
+            return;
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 136: {
+            A = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5392,10 +5975,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class RepeatedGroup_extension : pb::IMessage<RepeatedGroup_extension>, pb::IBufferMessage {
+  public sealed partial class RepeatedGroup_extension : pb::IMessage<RepeatedGroup_extension>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<RepeatedGroup_extension> _parser = new pb::MessageParser<RepeatedGroup_extension>(() => new RepeatedGroup_extension());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -5523,9 +6111,27 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          case 372:
+            return;
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 376: {
+            A = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5543,10 +6149,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestGroup : pb::IMessage<TestGroup>, pb::IBufferMessage {
+  public sealed partial class TestGroup : pb::IMessage<TestGroup>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestGroup> _parser = new pb::MessageParser<TestGroup>(() => new TestGroup());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -5712,9 +6323,32 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 131: {
+            if (!HasOptionalGroup) {
+              OptionalGroup = new global::Google.Protobuf.TestProtos.Proto2.TestGroup.Types.OptionalGroup();
+            }
+            input.ReadGroup(OptionalGroup);
+            break;
+          }
+          case 176: {
+            OptionalForeignEnum = (global::Google.Protobuf.TestProtos.Proto2.ForeignEnum) input.ReadEnum();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5737,12 +6371,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestGroup message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class OptionalGroup : pb::IMessage<OptionalGroup>, pb::IBufferMessage {
+      public sealed partial class OptionalGroup : pb::IMessage<OptionalGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<OptionalGroup> _parser = new pb::MessageParser<OptionalGroup>(() => new OptionalGroup());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -5870,9 +6509,27 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 132:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 136: {
+                A = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -5890,6 +6547,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -5898,7 +6556,11 @@
 
   }
 
-  public sealed partial class TestGroupExtension : pb::IExtendableMessage<TestGroupExtension>, pb::IBufferMessage {
+  public sealed partial class TestGroupExtension : pb::IExtendableMessage<TestGroupExtension>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestGroupExtension> _parser = new pb::MessageParser<TestGroupExtension>(() => new TestGroupExtension());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestGroupExtension> _extensions;
@@ -6003,9 +6665,23 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6019,6 +6695,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestGroupExtension, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -6044,7 +6721,11 @@
 
   }
 
-  public sealed partial class TestNestedExtension : pb::IMessage<TestNestedExtension>, pb::IBufferMessage {
+  public sealed partial class TestNestedExtension : pb::IMessage<TestNestedExtension>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestNestedExtension> _parser = new pb::MessageParser<TestNestedExtension>(() => new TestNestedExtension());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6133,9 +6814,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6147,12 +6840,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestNestedExtension message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class OptionalGroup_extension : pb::IMessage<OptionalGroup_extension>, pb::IBufferMessage {
+      public sealed partial class OptionalGroup_extension : pb::IMessage<OptionalGroup_extension>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<OptionalGroup_extension> _parser = new pb::MessageParser<OptionalGroup_extension>(() => new OptionalGroup_extension());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -6280,9 +6978,27 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 132:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 136: {
+                A = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -6300,6 +7016,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -6338,7 +7055,11 @@
   /// required filed because the code output is basically identical to
   /// optional fields for all types.
   /// </summary>
-  public sealed partial class TestRequired : pb::IMessage<TestRequired>, pb::IBufferMessage {
+  public sealed partial class TestRequired : pb::IMessage<TestRequired>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestRequired> _parser = new pb::MessageParser<TestRequired>(() => new TestRequired());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -7656,9 +8377,153 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            A = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            Dummy2 = input.ReadInt32();
+            break;
+          }
+          case 24: {
+            B = input.ReadInt32();
+            break;
+          }
+          case 32: {
+            Dummy4 = input.ReadInt32();
+            break;
+          }
+          case 40: {
+            Dummy5 = input.ReadInt32();
+            break;
+          }
+          case 48: {
+            Dummy6 = input.ReadInt32();
+            break;
+          }
+          case 56: {
+            Dummy7 = input.ReadInt32();
+            break;
+          }
+          case 64: {
+            Dummy8 = input.ReadInt32();
+            break;
+          }
+          case 72: {
+            Dummy9 = input.ReadInt32();
+            break;
+          }
+          case 80: {
+            Dummy10 = input.ReadInt32();
+            break;
+          }
+          case 88: {
+            Dummy11 = input.ReadInt32();
+            break;
+          }
+          case 96: {
+            Dummy12 = input.ReadInt32();
+            break;
+          }
+          case 104: {
+            Dummy13 = input.ReadInt32();
+            break;
+          }
+          case 112: {
+            Dummy14 = input.ReadInt32();
+            break;
+          }
+          case 120: {
+            Dummy15 = input.ReadInt32();
+            break;
+          }
+          case 128: {
+            Dummy16 = input.ReadInt32();
+            break;
+          }
+          case 136: {
+            Dummy17 = input.ReadInt32();
+            break;
+          }
+          case 144: {
+            Dummy18 = input.ReadInt32();
+            break;
+          }
+          case 152: {
+            Dummy19 = input.ReadInt32();
+            break;
+          }
+          case 160: {
+            Dummy20 = input.ReadInt32();
+            break;
+          }
+          case 168: {
+            Dummy21 = input.ReadInt32();
+            break;
+          }
+          case 176: {
+            Dummy22 = input.ReadInt32();
+            break;
+          }
+          case 184: {
+            Dummy23 = input.ReadInt32();
+            break;
+          }
+          case 192: {
+            Dummy24 = input.ReadInt32();
+            break;
+          }
+          case 200: {
+            Dummy25 = input.ReadInt32();
+            break;
+          }
+          case 208: {
+            Dummy26 = input.ReadInt32();
+            break;
+          }
+          case 216: {
+            Dummy27 = input.ReadInt32();
+            break;
+          }
+          case 224: {
+            Dummy28 = input.ReadInt32();
+            break;
+          }
+          case 232: {
+            Dummy29 = input.ReadInt32();
+            break;
+          }
+          case 240: {
+            Dummy30 = input.ReadInt32();
+            break;
+          }
+          case 248: {
+            Dummy31 = input.ReadInt32();
+            break;
+          }
+          case 256: {
+            Dummy32 = input.ReadInt32();
+            break;
+          }
+          case 264: {
+            C = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -7802,6 +8667,7 @@
         }
       }
     }
+    #endif
 
     #region Extensions
     /// <summary>Container for extensions for other messages declared in the TestRequired message type.</summary>
@@ -7816,7 +8682,11 @@
 
   }
 
-  public sealed partial class TestRequiredForeign : pb::IMessage<TestRequiredForeign>, pb::IBufferMessage {
+  public sealed partial class TestRequiredForeign : pb::IMessage<TestRequiredForeign>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestRequiredForeign> _parser = new pb::MessageParser<TestRequiredForeign>(() => new TestRequiredForeign());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -7987,9 +8857,36 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (optionalMessage_ == null) {
+              OptionalMessage = new global::Google.Protobuf.TestProtos.Proto2.TestRequired();
+            }
+            input.ReadMessage(OptionalMessage);
+            break;
+          }
+          case 18: {
+            repeatedMessage_.AddEntriesFrom(input, _repeated_repeatedMessage_codec);
+            break;
+          }
+          case 24: {
+            Dummy = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -8016,10 +8913,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestRequiredMessage : pb::IMessage<TestRequiredMessage>, pb::IBufferMessage {
+  public sealed partial class TestRequiredMessage : pb::IMessage<TestRequiredMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestRequiredMessage> _parser = new pb::MessageParser<TestRequiredMessage>(() => new TestRequiredMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -8178,9 +9080,39 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (optionalMessage_ == null) {
+              OptionalMessage = new global::Google.Protobuf.TestProtos.Proto2.TestRequired();
+            }
+            input.ReadMessage(OptionalMessage);
+            break;
+          }
+          case 18: {
+            repeatedMessage_.AddEntriesFrom(input, _repeated_repeatedMessage_codec);
+            break;
+          }
+          case 26: {
+            if (requiredMessage_ == null) {
+              RequiredMessage = new global::Google.Protobuf.TestProtos.Proto2.TestRequired();
+            }
+            input.ReadMessage(RequiredMessage);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -8210,13 +9142,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test that we can use NestedMessage from outside TestAllTypes.
   /// </summary>
-  public sealed partial class TestForeignNested : pb::IMessage<TestForeignNested>, pb::IBufferMessage {
+  public sealed partial class TestForeignNested : pb::IMessage<TestForeignNested>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestForeignNested> _parser = new pb::MessageParser<TestForeignNested>(() => new TestForeignNested());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -8332,9 +9269,28 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (foreignNested_ == null) {
+              ForeignNested = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes.Types.NestedMessage();
+            }
+            input.ReadMessage(ForeignNested);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -8353,13 +9309,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// TestEmptyMessage is used to test unknown field support.
   /// </summary>
-  public sealed partial class TestEmptyMessage : pb::IMessage<TestEmptyMessage>, pb::IBufferMessage {
+  public sealed partial class TestEmptyMessage : pb::IMessage<TestEmptyMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestEmptyMessage> _parser = new pb::MessageParser<TestEmptyMessage>(() => new TestEmptyMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -8448,9 +9409,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -8462,6 +9435,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -8469,7 +9443,11 @@
   /// Like above, but declare all field numbers as potential extensions.  No
   /// actual extensions should ever be defined for this type.
   /// </summary>
-  public sealed partial class TestEmptyMessageWithExtensions : pb::IExtendableMessage<TestEmptyMessageWithExtensions>, pb::IBufferMessage {
+  public sealed partial class TestEmptyMessageWithExtensions : pb::IExtendableMessage<TestEmptyMessageWithExtensions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestEmptyMessageWithExtensions> _parser = new pb::MessageParser<TestEmptyMessageWithExtensions>(() => new TestEmptyMessageWithExtensions());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestEmptyMessageWithExtensions> _extensions;
@@ -8574,9 +9552,23 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -8590,6 +9582,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestEmptyMessageWithExtensions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -8615,7 +9608,11 @@
 
   }
 
-  public sealed partial class TestMultipleExtensionRanges : pb::IExtendableMessage<TestMultipleExtensionRanges>, pb::IBufferMessage {
+  public sealed partial class TestMultipleExtensionRanges : pb::IExtendableMessage<TestMultipleExtensionRanges>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestMultipleExtensionRanges> _parser = new pb::MessageParser<TestMultipleExtensionRanges>(() => new TestMultipleExtensionRanges());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestMultipleExtensionRanges> _extensions;
@@ -8720,9 +9717,23 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -8736,6 +9747,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestMultipleExtensionRanges, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -8764,7 +9776,11 @@
   /// <summary>
   /// Test that really large tag numbers don't break anything.
   /// </summary>
-  public sealed partial class TestReallyLargeTagNumber : pb::IMessage<TestReallyLargeTagNumber>, pb::IBufferMessage {
+  public sealed partial class TestReallyLargeTagNumber : pb::IMessage<TestReallyLargeTagNumber>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestReallyLargeTagNumber> _parser = new pb::MessageParser<TestReallyLargeTagNumber>(() => new TestReallyLargeTagNumber());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -8933,9 +9949,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            A = input.ReadInt32();
+            break;
+          }
+          case 2147483640: {
+            Bb = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -8955,10 +9991,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestRecursiveMessage : pb::IMessage<TestRecursiveMessage>, pb::IBufferMessage {
+  public sealed partial class TestRecursiveMessage : pb::IMessage<TestRecursiveMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestRecursiveMessage> _parser = new pb::MessageParser<TestRecursiveMessage>(() => new TestRecursiveMessage());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -9113,9 +10154,32 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (a_ == null) {
+              A = new global::Google.Protobuf.TestProtos.Proto2.TestRecursiveMessage();
+            }
+            input.ReadMessage(A);
+            break;
+          }
+          case 16: {
+            I = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -9138,13 +10202,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test that mutual recursion works.
   /// </summary>
-  public sealed partial class TestMutualRecursionA : pb::IMessage<TestMutualRecursionA>, pb::IBufferMessage {
+  public sealed partial class TestMutualRecursionA : pb::IMessage<TestMutualRecursionA>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestMutualRecursionA> _parser = new pb::MessageParser<TestMutualRecursionA>(() => new TestMutualRecursionA());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -9298,9 +10367,35 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (bb_ == null) {
+              Bb = new global::Google.Protobuf.TestProtos.Proto2.TestMutualRecursionB();
+            }
+            input.ReadMessage(Bb);
+            break;
+          }
+          case 19: {
+            if (!HasSubGroup) {
+              SubGroup = new global::Google.Protobuf.TestProtos.Proto2.TestMutualRecursionA.Types.SubGroup();
+            }
+            input.ReadGroup(SubGroup);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -9326,12 +10421,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestMutualRecursionA message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class SubMessage : pb::IMessage<SubMessage>, pb::IBufferMessage {
+      public sealed partial class SubMessage : pb::IMessage<SubMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<SubMessage> _parser = new pb::MessageParser<SubMessage>(() => new SubMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -9447,9 +10547,28 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 10: {
+                if (b_ == null) {
+                  B = new global::Google.Protobuf.TestProtos.Proto2.TestMutualRecursionB();
+                }
+                input.ReadMessage(B);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -9468,10 +10587,15 @@
             }
           }
         }
+        #endif
 
       }
 
-      public sealed partial class SubGroup : pb::IMessage<SubGroup>, pb::IBufferMessage {
+      public sealed partial class SubGroup : pb::IMessage<SubGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<SubGroup> _parser = new pb::MessageParser<SubGroup>(() => new SubGroup());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -9617,9 +10741,37 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 20:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 26: {
+                if (subMessage_ == null) {
+                  SubMessage = new global::Google.Protobuf.TestProtos.Proto2.TestMutualRecursionA.Types.SubMessage();
+                }
+                input.ReadMessage(SubMessage);
+                break;
+              }
+              case 34: {
+                if (notInThisScc_ == null) {
+                  NotInThisScc = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+                }
+                input.ReadMessage(NotInThisScc);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -9647,6 +10799,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -9655,7 +10808,11 @@
 
   }
 
-  public sealed partial class TestMutualRecursionB : pb::IMessage<TestMutualRecursionB>, pb::IBufferMessage {
+  public sealed partial class TestMutualRecursionB : pb::IMessage<TestMutualRecursionB>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestMutualRecursionB> _parser = new pb::MessageParser<TestMutualRecursionB>(() => new TestMutualRecursionB());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -9810,9 +10967,32 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (a_ == null) {
+              A = new global::Google.Protobuf.TestProtos.Proto2.TestMutualRecursionA();
+            }
+            input.ReadMessage(A);
+            break;
+          }
+          case 16: {
+            OptionalInt32 = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -9835,10 +11015,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestIsInitialized : pb::IMessage<TestIsInitialized>, pb::IBufferMessage {
+  public sealed partial class TestIsInitialized : pb::IMessage<TestIsInitialized>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestIsInitialized> _parser = new pb::MessageParser<TestIsInitialized>(() => new TestIsInitialized());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -9954,9 +11139,28 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (subMessage_ == null) {
+              SubMessage = new global::Google.Protobuf.TestProtos.Proto2.TestIsInitialized.Types.SubMessage();
+            }
+            input.ReadMessage(SubMessage);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -9975,12 +11179,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestIsInitialized message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class SubMessage : pb::IMessage<SubMessage>, pb::IBufferMessage {
+      public sealed partial class SubMessage : pb::IMessage<SubMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<SubMessage> _parser = new pb::MessageParser<SubMessage>(() => new SubMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -10107,9 +11316,28 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 11: {
+                if (!HasSubGroup) {
+                  SubGroup = new global::Google.Protobuf.TestProtos.Proto2.TestIsInitialized.Types.SubMessage.Types.SubGroup();
+                }
+                input.ReadGroup(SubGroup);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -10128,12 +11356,17 @@
             }
           }
         }
+        #endif
 
         #region Nested types
         /// <summary>Container for nested types declared in the SubMessage message type.</summary>
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public static partial class Types {
-          public sealed partial class SubGroup : pb::IMessage<SubGroup>, pb::IBufferMessage {
+          public sealed partial class SubGroup : pb::IMessage<SubGroup>
+          #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+              , pb::IBufferMessage
+          #endif
+          {
             private static readonly pb::MessageParser<SubGroup> _parser = new pb::MessageParser<SubGroup>(() => new SubGroup());
             private pb::UnknownFieldSet _unknownFields;
             private int _hasBits0;
@@ -10261,9 +11494,27 @@
 
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
             public void MergeFrom(pb::CodedInputStream input) {
+            #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
               input.ReadRawMessage(this);
+            #else
+              uint tag;
+              while ((tag = input.ReadTag()) != 0) {
+                switch(tag) {
+                  case 12:
+                    return;
+                  default:
+                    _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                    break;
+                  case 16: {
+                    I = input.ReadInt32();
+                    break;
+                  }
+                }
+              }
+            #endif
             }
 
+            #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
             void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
               uint tag;
@@ -10281,6 +11532,7 @@
                 }
               }
             }
+            #endif
 
           }
 
@@ -10300,7 +11552,11 @@
   /// to compile with proto1, this will emit an error; so we only include it
   /// in protobuf_unittest_proto.
   /// </summary>
-  public sealed partial class TestDupFieldNumber : pb::IMessage<TestDupFieldNumber>, pb::IBufferMessage {
+  public sealed partial class TestDupFieldNumber : pb::IMessage<TestDupFieldNumber>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestDupFieldNumber> _parser = new pb::MessageParser<TestDupFieldNumber>(() => new TestDupFieldNumber());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -10507,9 +11763,39 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            A = input.ReadInt32();
+            break;
+          }
+          case 19: {
+            if (!HasFoo) {
+              Foo = new global::Google.Protobuf.TestProtos.Proto2.TestDupFieldNumber.Types.Foo();
+            }
+            input.ReadGroup(Foo);
+            break;
+          }
+          case 27: {
+            if (!HasBar) {
+              Bar = new global::Google.Protobuf.TestProtos.Proto2.TestDupFieldNumber.Types.Bar();
+            }
+            input.ReadGroup(Bar);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -10539,12 +11825,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestDupFieldNumber message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class Foo : pb::IMessage<Foo>, pb::IBufferMessage {
+      public sealed partial class Foo : pb::IMessage<Foo>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<Foo> _parser = new pb::MessageParser<Foo>(() => new Foo());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -10672,9 +11963,27 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 20:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                A = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -10692,10 +12001,15 @@
             }
           }
         }
+        #endif
 
       }
 
-      public sealed partial class Bar : pb::IMessage<Bar>, pb::IBufferMessage {
+      public sealed partial class Bar : pb::IMessage<Bar>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<Bar> _parser = new pb::MessageParser<Bar>(() => new Bar());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -10823,9 +12137,27 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 28:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                A = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -10843,6 +12175,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -10854,7 +12187,11 @@
   /// <summary>
   /// Additional messages for testing lazy fields.
   /// </summary>
-  public sealed partial class TestEagerMessage : pb::IMessage<TestEagerMessage>, pb::IBufferMessage {
+  public sealed partial class TestEagerMessage : pb::IMessage<TestEagerMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestEagerMessage> _parser = new pb::MessageParser<TestEagerMessage>(() => new TestEagerMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -10970,9 +12307,28 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (subMessage_ == null) {
+              SubMessage = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+            }
+            input.ReadMessage(SubMessage);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -10991,10 +12347,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestLazyMessage : pb::IMessage<TestLazyMessage>, pb::IBufferMessage {
+  public sealed partial class TestLazyMessage : pb::IMessage<TestLazyMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestLazyMessage> _parser = new pb::MessageParser<TestLazyMessage>(() => new TestLazyMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -11110,9 +12471,28 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (subMessage_ == null) {
+              SubMessage = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+            }
+            input.ReadMessage(SubMessage);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -11131,13 +12511,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Needed for a Python test.
   /// </summary>
-  public sealed partial class TestNestedMessageHasBits : pb::IMessage<TestNestedMessageHasBits>, pb::IBufferMessage {
+  public sealed partial class TestNestedMessageHasBits : pb::IMessage<TestNestedMessageHasBits>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestNestedMessageHasBits> _parser = new pb::MessageParser<TestNestedMessageHasBits>(() => new TestNestedMessageHasBits());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -11253,9 +12638,28 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (optionalNestedMessage_ == null) {
+              OptionalNestedMessage = new global::Google.Protobuf.TestProtos.Proto2.TestNestedMessageHasBits.Types.NestedMessage();
+            }
+            input.ReadMessage(OptionalNestedMessage);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -11274,12 +12678,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestNestedMessageHasBits message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -11400,9 +12809,30 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 10:
+              case 8: {
+                nestedmessageRepeatedInt32_.AddEntriesFrom(input, _repeated_nestedmessageRepeatedInt32_codec);
+                break;
+              }
+              case 18: {
+                nestedmessageRepeatedForeignmessage_.AddEntriesFrom(input, _repeated_nestedmessageRepeatedForeignmessage_codec);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -11423,6 +12853,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -11435,7 +12866,11 @@
   /// Test message with CamelCase field names.  This violates Protocol Buffer
   /// standard style.
   /// </summary>
-  public sealed partial class TestCamelCaseFieldNames : pb::IMessage<TestCamelCaseFieldNames>, pb::IBufferMessage {
+  public sealed partial class TestCamelCaseFieldNames : pb::IMessage<TestCamelCaseFieldNames>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestCamelCaseFieldNames> _parser = new pb::MessageParser<TestCamelCaseFieldNames>(() => new TestCamelCaseFieldNames());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -11831,9 +13266,74 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            PrimitiveField = input.ReadInt32();
+            break;
+          }
+          case 18: {
+            StringField = input.ReadString();
+            break;
+          }
+          case 24: {
+            EnumField = (global::Google.Protobuf.TestProtos.Proto2.ForeignEnum) input.ReadEnum();
+            break;
+          }
+          case 34: {
+            if (messageField_ == null) {
+              MessageField = new global::Google.Protobuf.TestProtos.Proto2.ForeignMessage();
+            }
+            input.ReadMessage(MessageField);
+            break;
+          }
+          case 42: {
+            StringPieceField = input.ReadString();
+            break;
+          }
+          case 50: {
+            CordField = input.ReadString();
+            break;
+          }
+          case 58:
+          case 56: {
+            repeatedPrimitiveField_.AddEntriesFrom(input, _repeated_repeatedPrimitiveField_codec);
+            break;
+          }
+          case 66: {
+            repeatedStringField_.AddEntriesFrom(input, _repeated_repeatedStringField_codec);
+            break;
+          }
+          case 74:
+          case 72: {
+            repeatedEnumField_.AddEntriesFrom(input, _repeated_repeatedEnumField_codec);
+            break;
+          }
+          case 82: {
+            repeatedMessageField_.AddEntriesFrom(input, _repeated_repeatedMessageField_codec);
+            break;
+          }
+          case 90: {
+            repeatedStringPieceField_.AddEntriesFrom(input, _repeated_repeatedStringPieceField_codec);
+            break;
+          }
+          case 98: {
+            repeatedCordField_.AddEntriesFrom(input, _repeated_repeatedCordField_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -11898,6 +13398,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -11905,7 +13406,11 @@
   /// We list fields out of order, to ensure that we're using field number and not
   /// field index to determine serialization order.
   /// </summary>
-  public sealed partial class TestFieldOrderings : pb::IExtendableMessage<TestFieldOrderings>, pb::IBufferMessage {
+  public sealed partial class TestFieldOrderings : pb::IExtendableMessage<TestFieldOrderings>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestFieldOrderings> _parser = new pb::MessageParser<TestFieldOrderings>(() => new TestFieldOrderings());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestFieldOrderings> _extensions;
@@ -12149,9 +13654,42 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 8: {
+            MyInt = input.ReadInt64();
+            break;
+          }
+          case 90: {
+            MyString = input.ReadString();
+            break;
+          }
+          case 813: {
+            MyFloat = input.ReadFloat();
+            break;
+          }
+          case 1602: {
+            if (optionalNestedMessage_ == null) {
+              OptionalNestedMessage = new global::Google.Protobuf.TestProtos.Proto2.TestFieldOrderings.Types.NestedMessage();
+            }
+            input.ReadMessage(OptionalNestedMessage);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -12184,6 +13722,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestFieldOrderings, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -12211,7 +13750,11 @@
     /// <summary>Container for nested types declared in the TestFieldOrderings message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -12381,9 +13924,29 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                Bb = input.ReadInt32();
+                break;
+              }
+              case 16: {
+                Oo = input.ReadInt64();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -12403,6 +13966,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -12411,7 +13975,11 @@
 
   }
 
-  public sealed partial class TestExtensionOrderings1 : pb::IMessage<TestExtensionOrderings1>, pb::IBufferMessage {
+  public sealed partial class TestExtensionOrderings1 : pb::IMessage<TestExtensionOrderings1>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestExtensionOrderings1> _parser = new pb::MessageParser<TestExtensionOrderings1>(() => new TestExtensionOrderings1());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -12536,9 +14104,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            MyString = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -12554,6 +14138,7 @@
         }
       }
     }
+    #endif
 
     #region Extensions
     /// <summary>Container for extensions for other messages declared in the TestExtensionOrderings1 message type.</summary>
@@ -12566,7 +14151,11 @@
 
   }
 
-  public sealed partial class TestExtensionOrderings2 : pb::IMessage<TestExtensionOrderings2>, pb::IBufferMessage {
+  public sealed partial class TestExtensionOrderings2 : pb::IMessage<TestExtensionOrderings2>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestExtensionOrderings2> _parser = new pb::MessageParser<TestExtensionOrderings2>(() => new TestExtensionOrderings2());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -12691,9 +14280,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            MyString = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -12709,12 +14314,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestExtensionOrderings2 message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class TestExtensionOrderings3 : pb::IMessage<TestExtensionOrderings3>, pb::IBufferMessage {
+      public sealed partial class TestExtensionOrderings3 : pb::IMessage<TestExtensionOrderings3>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<TestExtensionOrderings3> _parser = new pb::MessageParser<TestExtensionOrderings3>(() => new TestExtensionOrderings3());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -12839,9 +14449,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 10: {
+                MyString = input.ReadString();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -12857,6 +14483,7 @@
             }
           }
         }
+        #endif
 
         #region Extensions
         /// <summary>Container for extensions for other messages declared in the TestExtensionOrderings3 message type.</summary>
@@ -12883,7 +14510,11 @@
 
   }
 
-  public sealed partial class TestExtremeDefaultValues : pb::IMessage<TestExtremeDefaultValues>, pb::IBufferMessage {
+  public sealed partial class TestExtremeDefaultValues : pb::IMessage<TestExtremeDefaultValues>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestExtremeDefaultValues> _parser = new pb::MessageParser<TestExtremeDefaultValues>(() => new TestExtremeDefaultValues());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -13989,9 +15620,129 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            EscapedBytes = input.ReadBytes();
+            break;
+          }
+          case 16: {
+            LargeUint32 = input.ReadUInt32();
+            break;
+          }
+          case 24: {
+            LargeUint64 = input.ReadUInt64();
+            break;
+          }
+          case 32: {
+            SmallInt32 = input.ReadInt32();
+            break;
+          }
+          case 40: {
+            SmallInt64 = input.ReadInt64();
+            break;
+          }
+          case 50: {
+            Utf8String = input.ReadString();
+            break;
+          }
+          case 61: {
+            ZeroFloat = input.ReadFloat();
+            break;
+          }
+          case 69: {
+            OneFloat = input.ReadFloat();
+            break;
+          }
+          case 77: {
+            SmallFloat = input.ReadFloat();
+            break;
+          }
+          case 85: {
+            NegativeOneFloat = input.ReadFloat();
+            break;
+          }
+          case 93: {
+            NegativeFloat = input.ReadFloat();
+            break;
+          }
+          case 101: {
+            LargeFloat = input.ReadFloat();
+            break;
+          }
+          case 109: {
+            SmallNegativeFloat = input.ReadFloat();
+            break;
+          }
+          case 113: {
+            InfDouble = input.ReadDouble();
+            break;
+          }
+          case 121: {
+            NegInfDouble = input.ReadDouble();
+            break;
+          }
+          case 129: {
+            NanDouble = input.ReadDouble();
+            break;
+          }
+          case 141: {
+            InfFloat = input.ReadFloat();
+            break;
+          }
+          case 149: {
+            NegInfFloat = input.ReadFloat();
+            break;
+          }
+          case 157: {
+            NanFloat = input.ReadFloat();
+            break;
+          }
+          case 162: {
+            CppTrigraph = input.ReadString();
+            break;
+          }
+          case 168: {
+            ReallySmallInt32 = input.ReadInt32();
+            break;
+          }
+          case 176: {
+            ReallySmallInt64 = input.ReadInt64();
+            break;
+          }
+          case 186: {
+            StringWithZero = input.ReadString();
+            break;
+          }
+          case 194: {
+            BytesWithZero = input.ReadBytes();
+            break;
+          }
+          case 202: {
+            StringPieceWithZero = input.ReadString();
+            break;
+          }
+          case 210: {
+            CordWithZero = input.ReadString();
+            break;
+          }
+          case 218: {
+            ReplacementString = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -14111,10 +15862,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class SparseEnumMessage : pb::IMessage<SparseEnumMessage>, pb::IBufferMessage {
+  public sealed partial class SparseEnumMessage : pb::IMessage<SparseEnumMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<SparseEnumMessage> _parser = new pb::MessageParser<SparseEnumMessage>(() => new SparseEnumMessage());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -14242,9 +15998,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            SparseEnum = (global::Google.Protobuf.TestProtos.Proto2.TestSparseEnum) input.ReadEnum();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -14260,13 +16032,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test String and Bytes: string is for valid UTF-8 strings
   /// </summary>
-  public sealed partial class OneString : pb::IMessage<OneString>, pb::IBufferMessage {
+  public sealed partial class OneString : pb::IMessage<OneString>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<OneString> _parser = new pb::MessageParser<OneString>(() => new OneString());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -14391,9 +16168,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Data = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -14409,10 +16202,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class MoreString : pb::IMessage<MoreString>, pb::IBufferMessage {
+  public sealed partial class MoreString : pb::IMessage<MoreString>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<MoreString> _parser = new pb::MessageParser<MoreString>(() => new MoreString());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -14517,9 +16315,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            data_.AddEntriesFrom(input, _repeated_data_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -14535,10 +16349,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class OneBytes : pb::IMessage<OneBytes>, pb::IBufferMessage {
+  public sealed partial class OneBytes : pb::IMessage<OneBytes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<OneBytes> _parser = new pb::MessageParser<OneBytes>(() => new OneBytes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -14663,9 +16482,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Data = input.ReadBytes();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -14681,10 +16516,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class MoreBytes : pb::IMessage<MoreBytes>, pb::IBufferMessage {
+  public sealed partial class MoreBytes : pb::IMessage<MoreBytes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<MoreBytes> _parser = new pb::MessageParser<MoreBytes>(() => new MoreBytes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -14789,9 +16629,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            data_.AddEntriesFrom(input, _repeated_data_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -14807,13 +16663,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test int32, uint32, int64, uint64, and bool are all compatible
   /// </summary>
-  public sealed partial class Int32Message : pb::IMessage<Int32Message>, pb::IBufferMessage {
+  public sealed partial class Int32Message : pb::IMessage<Int32Message>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Int32Message> _parser = new pb::MessageParser<Int32Message>(() => new Int32Message());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -14941,9 +16802,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Data = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -14959,10 +16836,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class Uint32Message : pb::IMessage<Uint32Message>, pb::IBufferMessage {
+  public sealed partial class Uint32Message : pb::IMessage<Uint32Message>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Uint32Message> _parser = new pb::MessageParser<Uint32Message>(() => new Uint32Message());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -15090,9 +16972,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Data = input.ReadUInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -15108,10 +17006,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class Int64Message : pb::IMessage<Int64Message>, pb::IBufferMessage {
+  public sealed partial class Int64Message : pb::IMessage<Int64Message>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Int64Message> _parser = new pb::MessageParser<Int64Message>(() => new Int64Message());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -15239,9 +17142,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Data = input.ReadInt64();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -15257,10 +17176,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class Uint64Message : pb::IMessage<Uint64Message>, pb::IBufferMessage {
+  public sealed partial class Uint64Message : pb::IMessage<Uint64Message>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Uint64Message> _parser = new pb::MessageParser<Uint64Message>(() => new Uint64Message());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -15388,9 +17312,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Data = input.ReadUInt64();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -15406,10 +17346,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class BoolMessage : pb::IMessage<BoolMessage>, pb::IBufferMessage {
+  public sealed partial class BoolMessage : pb::IMessage<BoolMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<BoolMessage> _parser = new pb::MessageParser<BoolMessage>(() => new BoolMessage());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -15537,9 +17482,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Data = input.ReadBool();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -15555,13 +17516,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test oneofs.
   /// </summary>
-  public sealed partial class TestOneof : pb::IMessage<TestOneof>, pb::IBufferMessage {
+  public sealed partial class TestOneof : pb::IMessage<TestOneof>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestOneof> _parser = new pb::MessageParser<TestOneof>(() => new TestOneof());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -15826,9 +17792,47 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            FooInt = input.ReadInt32();
+            break;
+          }
+          case 18: {
+            FooString = input.ReadString();
+            break;
+          }
+          case 26: {
+            global::Google.Protobuf.TestProtos.Proto2.TestAllTypes subBuilder = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+            if (fooCase_ == FooOneofCase.FooMessage) {
+              subBuilder.MergeFrom(FooMessage);
+            }
+            input.ReadMessage(subBuilder);
+            FooMessage = subBuilder;
+            break;
+          }
+          case 35: {
+            global::Google.Protobuf.TestProtos.Proto2.TestOneof.Types.FooGroup subBuilder = new global::Google.Protobuf.TestProtos.Proto2.TestOneof.Types.FooGroup();
+            if (HasFooGroup) {
+              subBuilder.MergeFrom(FooGroup);
+            }
+            input.ReadGroup(subBuilder);
+            FooGroup = subBuilder;
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -15866,12 +17870,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestOneof message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class FooGroup : pb::IMessage<FooGroup>, pb::IBufferMessage {
+      public sealed partial class FooGroup : pb::IMessage<FooGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<FooGroup> _parser = new pb::MessageParser<FooGroup>(() => new FooGroup());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -16035,9 +18044,31 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 36:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 40: {
+                A = input.ReadInt32();
+                break;
+              }
+              case 50: {
+                B = input.ReadString();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -16059,6 +18090,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -16067,7 +18099,11 @@
 
   }
 
-  public sealed partial class TestOneofBackwardsCompatible : pb::IMessage<TestOneofBackwardsCompatible>, pb::IBufferMessage {
+  public sealed partial class TestOneofBackwardsCompatible : pb::IMessage<TestOneofBackwardsCompatible>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestOneofBackwardsCompatible> _parser = new pb::MessageParser<TestOneofBackwardsCompatible>(() => new TestOneofBackwardsCompatible());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -16296,9 +18332,43 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            FooInt = input.ReadInt32();
+            break;
+          }
+          case 18: {
+            FooString = input.ReadString();
+            break;
+          }
+          case 26: {
+            if (fooMessage_ == null) {
+              FooMessage = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+            }
+            input.ReadMessage(FooMessage);
+            break;
+          }
+          case 35: {
+            if (!HasFooGroup) {
+              FooGroup = new global::Google.Protobuf.TestProtos.Proto2.TestOneofBackwardsCompatible.Types.FooGroup();
+            }
+            input.ReadGroup(FooGroup);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -16332,12 +18402,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestOneofBackwardsCompatible message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class FooGroup : pb::IMessage<FooGroup>, pb::IBufferMessage {
+      public sealed partial class FooGroup : pb::IMessage<FooGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<FooGroup> _parser = new pb::MessageParser<FooGroup>(() => new FooGroup());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -16501,9 +18576,31 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 36:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 40: {
+                A = input.ReadInt32();
+                break;
+              }
+              case 50: {
+                B = input.ReadString();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -16525,6 +18622,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -16533,7 +18631,11 @@
 
   }
 
-  public sealed partial class TestOneof2 : pb::IMessage<TestOneof2>, pb::IBufferMessage {
+  public sealed partial class TestOneof2 : pb::IMessage<TestOneof2>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestOneof2> _parser = new pb::MessageParser<TestOneof2>(() => new TestOneof2());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -17318,9 +19420,106 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            FooInt = input.ReadInt32();
+            break;
+          }
+          case 18: {
+            FooString = input.ReadString();
+            break;
+          }
+          case 26: {
+            FooCord = input.ReadString();
+            break;
+          }
+          case 34: {
+            FooStringPiece = input.ReadString();
+            break;
+          }
+          case 42: {
+            FooBytes = input.ReadBytes();
+            break;
+          }
+          case 48: {
+            foo_ = input.ReadEnum();
+            fooCase_ = FooOneofCase.FooEnum;
+            break;
+          }
+          case 58: {
+            global::Google.Protobuf.TestProtos.Proto2.TestOneof2.Types.NestedMessage subBuilder = new global::Google.Protobuf.TestProtos.Proto2.TestOneof2.Types.NestedMessage();
+            if (fooCase_ == FooOneofCase.FooMessage) {
+              subBuilder.MergeFrom(FooMessage);
+            }
+            input.ReadMessage(subBuilder);
+            FooMessage = subBuilder;
+            break;
+          }
+          case 67: {
+            global::Google.Protobuf.TestProtos.Proto2.TestOneof2.Types.FooGroup subBuilder = new global::Google.Protobuf.TestProtos.Proto2.TestOneof2.Types.FooGroup();
+            if (HasFooGroup) {
+              subBuilder.MergeFrom(FooGroup);
+            }
+            input.ReadGroup(subBuilder);
+            FooGroup = subBuilder;
+            break;
+          }
+          case 90: {
+            global::Google.Protobuf.TestProtos.Proto2.TestOneof2.Types.NestedMessage subBuilder = new global::Google.Protobuf.TestProtos.Proto2.TestOneof2.Types.NestedMessage();
+            if (fooCase_ == FooOneofCase.FooLazyMessage) {
+              subBuilder.MergeFrom(FooLazyMessage);
+            }
+            input.ReadMessage(subBuilder);
+            FooLazyMessage = subBuilder;
+            break;
+          }
+          case 96: {
+            BarInt = input.ReadInt32();
+            break;
+          }
+          case 106: {
+            BarString = input.ReadString();
+            break;
+          }
+          case 114: {
+            BarCord = input.ReadString();
+            break;
+          }
+          case 122: {
+            BarStringPiece = input.ReadString();
+            break;
+          }
+          case 130: {
+            BarBytes = input.ReadBytes();
+            break;
+          }
+          case 136: {
+            bar_ = input.ReadEnum();
+            barCase_ = BarOneofCase.BarEnum;
+            break;
+          }
+          case 144: {
+            BazInt = input.ReadInt32();
+            break;
+          }
+          case 154: {
+            BazString = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -17417,6 +19616,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestOneof2 message type.</summary>
@@ -17428,7 +19628,11 @@
         [pbr::OriginalName("BAZ")] Baz = 3,
       }
 
-      public sealed partial class FooGroup : pb::IMessage<FooGroup>, pb::IBufferMessage {
+      public sealed partial class FooGroup : pb::IMessage<FooGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<FooGroup> _parser = new pb::MessageParser<FooGroup>(() => new FooGroup());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -17592,9 +19796,31 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 68:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 72: {
+                A = input.ReadInt32();
+                break;
+              }
+              case 82: {
+                B = input.ReadString();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -17616,10 +19842,15 @@
             }
           }
         }
+        #endif
 
       }
 
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -17763,9 +19994,30 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                QuxInt = input.ReadInt64();
+                break;
+              }
+              case 18:
+              case 16: {
+                corgeInt_.AddEntriesFrom(input, _repeated_corgeInt_codec);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -17786,6 +20038,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -17794,7 +20047,11 @@
 
   }
 
-  public sealed partial class TestRequiredOneof : pb::IMessage<TestRequiredOneof>, pb::IBufferMessage {
+  public sealed partial class TestRequiredOneof : pb::IMessage<TestRequiredOneof>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestRequiredOneof> _parser = new pb::MessageParser<TestRequiredOneof>(() => new TestRequiredOneof());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -18016,9 +20273,38 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            FooInt = input.ReadInt32();
+            break;
+          }
+          case 18: {
+            FooString = input.ReadString();
+            break;
+          }
+          case 26: {
+            global::Google.Protobuf.TestProtos.Proto2.TestRequiredOneof.Types.NestedMessage subBuilder = new global::Google.Protobuf.TestProtos.Proto2.TestRequiredOneof.Types.NestedMessage();
+            if (fooCase_ == FooOneofCase.FooMessage) {
+              subBuilder.MergeFrom(FooMessage);
+            }
+            input.ReadMessage(subBuilder);
+            FooMessage = subBuilder;
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -18047,12 +20333,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestRequiredOneof message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -18180,9 +20471,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 9: {
+                RequiredDouble = input.ReadDouble();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -18198,6 +20505,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -18206,7 +20514,11 @@
 
   }
 
-  public sealed partial class TestRequiredMap : pb::IMessage<TestRequiredMap>, pb::IBufferMessage {
+  public sealed partial class TestRequiredMap : pb::IMessage<TestRequiredMap>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestRequiredMap> _parser = new pb::MessageParser<TestRequiredMap>(() => new TestRequiredMap());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -18311,9 +20623,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            foo_.AddEntriesFrom(input, _map_foo_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -18329,12 +20657,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestRequiredMap message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -18462,9 +20795,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                RequiredInt32 = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -18480,6 +20829,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -18488,7 +20838,11 @@
 
   }
 
-  public sealed partial class TestPackedTypes : pb::IMessage<TestPackedTypes>, pb::IBufferMessage {
+  public sealed partial class TestPackedTypes : pb::IMessage<TestPackedTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestPackedTypes> _parser = new pb::MessageParser<TestPackedTypes>(() => new TestPackedTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -18801,9 +21155,91 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 722:
+          case 720: {
+            packedInt32_.AddEntriesFrom(input, _repeated_packedInt32_codec);
+            break;
+          }
+          case 730:
+          case 728: {
+            packedInt64_.AddEntriesFrom(input, _repeated_packedInt64_codec);
+            break;
+          }
+          case 738:
+          case 736: {
+            packedUint32_.AddEntriesFrom(input, _repeated_packedUint32_codec);
+            break;
+          }
+          case 746:
+          case 744: {
+            packedUint64_.AddEntriesFrom(input, _repeated_packedUint64_codec);
+            break;
+          }
+          case 754:
+          case 752: {
+            packedSint32_.AddEntriesFrom(input, _repeated_packedSint32_codec);
+            break;
+          }
+          case 762:
+          case 760: {
+            packedSint64_.AddEntriesFrom(input, _repeated_packedSint64_codec);
+            break;
+          }
+          case 770:
+          case 773: {
+            packedFixed32_.AddEntriesFrom(input, _repeated_packedFixed32_codec);
+            break;
+          }
+          case 778:
+          case 777: {
+            packedFixed64_.AddEntriesFrom(input, _repeated_packedFixed64_codec);
+            break;
+          }
+          case 786:
+          case 789: {
+            packedSfixed32_.AddEntriesFrom(input, _repeated_packedSfixed32_codec);
+            break;
+          }
+          case 794:
+          case 793: {
+            packedSfixed64_.AddEntriesFrom(input, _repeated_packedSfixed64_codec);
+            break;
+          }
+          case 802:
+          case 805: {
+            packedFloat_.AddEntriesFrom(input, _repeated_packedFloat_codec);
+            break;
+          }
+          case 810:
+          case 809: {
+            packedDouble_.AddEntriesFrom(input, _repeated_packedDouble_codec);
+            break;
+          }
+          case 818:
+          case 816: {
+            packedBool_.AddEntriesFrom(input, _repeated_packedBool_codec);
+            break;
+          }
+          case 826:
+          case 824: {
+            packedEnum_.AddEntriesFrom(input, _repeated_packedEnum_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -18885,6 +21321,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -18892,7 +21329,11 @@
   /// A message with the same fields as TestPackedTypes, but without packing. Used
   /// to test packed &lt;-> unpacked wire compatibility.
   /// </summary>
-  public sealed partial class TestUnpackedTypes : pb::IMessage<TestUnpackedTypes>, pb::IBufferMessage {
+  public sealed partial class TestUnpackedTypes : pb::IMessage<TestUnpackedTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestUnpackedTypes> _parser = new pb::MessageParser<TestUnpackedTypes>(() => new TestUnpackedTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -19205,9 +21646,91 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 722:
+          case 720: {
+            unpackedInt32_.AddEntriesFrom(input, _repeated_unpackedInt32_codec);
+            break;
+          }
+          case 730:
+          case 728: {
+            unpackedInt64_.AddEntriesFrom(input, _repeated_unpackedInt64_codec);
+            break;
+          }
+          case 738:
+          case 736: {
+            unpackedUint32_.AddEntriesFrom(input, _repeated_unpackedUint32_codec);
+            break;
+          }
+          case 746:
+          case 744: {
+            unpackedUint64_.AddEntriesFrom(input, _repeated_unpackedUint64_codec);
+            break;
+          }
+          case 754:
+          case 752: {
+            unpackedSint32_.AddEntriesFrom(input, _repeated_unpackedSint32_codec);
+            break;
+          }
+          case 762:
+          case 760: {
+            unpackedSint64_.AddEntriesFrom(input, _repeated_unpackedSint64_codec);
+            break;
+          }
+          case 770:
+          case 773: {
+            unpackedFixed32_.AddEntriesFrom(input, _repeated_unpackedFixed32_codec);
+            break;
+          }
+          case 778:
+          case 777: {
+            unpackedFixed64_.AddEntriesFrom(input, _repeated_unpackedFixed64_codec);
+            break;
+          }
+          case 786:
+          case 789: {
+            unpackedSfixed32_.AddEntriesFrom(input, _repeated_unpackedSfixed32_codec);
+            break;
+          }
+          case 794:
+          case 793: {
+            unpackedSfixed64_.AddEntriesFrom(input, _repeated_unpackedSfixed64_codec);
+            break;
+          }
+          case 802:
+          case 805: {
+            unpackedFloat_.AddEntriesFrom(input, _repeated_unpackedFloat_codec);
+            break;
+          }
+          case 810:
+          case 809: {
+            unpackedDouble_.AddEntriesFrom(input, _repeated_unpackedDouble_codec);
+            break;
+          }
+          case 818:
+          case 816: {
+            unpackedBool_.AddEntriesFrom(input, _repeated_unpackedBool_codec);
+            break;
+          }
+          case 826:
+          case 824: {
+            unpackedEnum_.AddEntriesFrom(input, _repeated_unpackedEnum_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -19289,10 +21812,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestPackedExtensions : pb::IExtendableMessage<TestPackedExtensions>, pb::IBufferMessage {
+  public sealed partial class TestPackedExtensions : pb::IExtendableMessage<TestPackedExtensions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestPackedExtensions> _parser = new pb::MessageParser<TestPackedExtensions>(() => new TestPackedExtensions());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestPackedExtensions> _extensions;
@@ -19397,9 +21925,23 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -19413,6 +21955,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestPackedExtensions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -19438,7 +21981,11 @@
 
   }
 
-  public sealed partial class TestUnpackedExtensions : pb::IExtendableMessage<TestUnpackedExtensions>, pb::IBufferMessage {
+  public sealed partial class TestUnpackedExtensions : pb::IExtendableMessage<TestUnpackedExtensions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestUnpackedExtensions> _parser = new pb::MessageParser<TestUnpackedExtensions>(() => new TestUnpackedExtensions());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestUnpackedExtensions> _extensions;
@@ -19543,9 +22090,23 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -19559,6 +22120,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestUnpackedExtensions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -19589,7 +22151,11 @@
   /// a set of extensions to TestAllExtensions dynamically, based on the fields
   /// of this message type.
   /// </summary>
-  public sealed partial class TestDynamicExtensions : pb::IMessage<TestDynamicExtensions>, pb::IBufferMessage {
+  public sealed partial class TestDynamicExtensions : pb::IMessage<TestDynamicExtensions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestDynamicExtensions> _parser = new pb::MessageParser<TestDynamicExtensions>(() => new TestDynamicExtensions());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -19877,9 +22443,56 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 16005: {
+            ScalarExtension = input.ReadFixed32();
+            break;
+          }
+          case 16008: {
+            EnumExtension = (global::Google.Protobuf.TestProtos.Proto2.ForeignEnum) input.ReadEnum();
+            break;
+          }
+          case 16016: {
+            DynamicEnumExtension = (global::Google.Protobuf.TestProtos.Proto2.TestDynamicExtensions.Types.DynamicEnumType) input.ReadEnum();
+            break;
+          }
+          case 16026: {
+            if (messageExtension_ == null) {
+              MessageExtension = new global::Google.Protobuf.TestProtos.Proto2.ForeignMessage();
+            }
+            input.ReadMessage(MessageExtension);
+            break;
+          }
+          case 16034: {
+            if (dynamicMessageExtension_ == null) {
+              DynamicMessageExtension = new global::Google.Protobuf.TestProtos.Proto2.TestDynamicExtensions.Types.DynamicMessageType();
+            }
+            input.ReadMessage(DynamicMessageExtension);
+            break;
+          }
+          case 16042: {
+            repeatedExtension_.AddEntriesFrom(input, _repeated_repeatedExtension_codec);
+            break;
+          }
+          case 16050:
+          case 16048: {
+            packedExtension_.AddEntriesFrom(input, _repeated_packedExtension_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -19926,6 +22539,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestDynamicExtensions message type.</summary>
@@ -19937,7 +22551,11 @@
         [pbr::OriginalName("DYNAMIC_BAZ")] DynamicBaz = 2202,
       }
 
-      public sealed partial class DynamicMessageType : pb::IMessage<DynamicMessageType>, pb::IBufferMessage {
+      public sealed partial class DynamicMessageType : pb::IMessage<DynamicMessageType>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<DynamicMessageType> _parser = new pb::MessageParser<DynamicMessageType>(() => new DynamicMessageType());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -20065,9 +22683,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 16800: {
+                DynamicField = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -20083,6 +22717,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -20091,7 +22726,11 @@
 
   }
 
-  public sealed partial class TestRepeatedScalarDifferentTagSizes : pb::IMessage<TestRepeatedScalarDifferentTagSizes>, pb::IBufferMessage {
+  public sealed partial class TestRepeatedScalarDifferentTagSizes : pb::IMessage<TestRepeatedScalarDifferentTagSizes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestRepeatedScalarDifferentTagSizes> _parser = new pb::MessageParser<TestRepeatedScalarDifferentTagSizes>(() => new TestRepeatedScalarDifferentTagSizes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -20290,9 +22929,51 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 98:
+          case 101: {
+            repeatedFixed32_.AddEntriesFrom(input, _repeated_repeatedFixed32_codec);
+            break;
+          }
+          case 106:
+          case 104: {
+            repeatedInt32_.AddEntriesFrom(input, _repeated_repeatedInt32_codec);
+            break;
+          }
+          case 16370:
+          case 16369: {
+            repeatedFixed64_.AddEntriesFrom(input, _repeated_repeatedFixed64_codec);
+            break;
+          }
+          case 16378:
+          case 16376: {
+            repeatedInt64_.AddEntriesFrom(input, _repeated_repeatedInt64_codec);
+            break;
+          }
+          case 2097138:
+          case 2097141: {
+            repeatedFloat_.AddEntriesFrom(input, _repeated_repeatedFloat_codec);
+            break;
+          }
+          case 2097146:
+          case 2097144: {
+            repeatedUint64_.AddEntriesFrom(input, _repeated_repeatedUint64_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -20334,6 +23015,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -20341,7 +23023,11 @@
   /// Test that if an optional or required message/group field appears multiple
   /// times in the input, they need to be merged.
   /// </summary>
-  public sealed partial class TestParsingMerge : pb::IExtendableMessage<TestParsingMerge>, pb::IBufferMessage {
+  public sealed partial class TestParsingMerge : pb::IExtendableMessage<TestParsingMerge>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestParsingMerge> _parser = new pb::MessageParser<TestParsingMerge>(() => new TestParsingMerge());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestParsingMerge> _extensions;
@@ -20570,9 +23256,52 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 10: {
+            if (requiredAllTypes_ == null) {
+              RequiredAllTypes = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+            }
+            input.ReadMessage(RequiredAllTypes);
+            break;
+          }
+          case 18: {
+            if (optionalAllTypes_ == null) {
+              OptionalAllTypes = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+            }
+            input.ReadMessage(OptionalAllTypes);
+            break;
+          }
+          case 26: {
+            repeatedAllTypes_.AddEntriesFrom(input, _repeated_repeatedAllTypes_codec);
+            break;
+          }
+          case 83: {
+            if (!HasOptionalGroup) {
+              OptionalGroup = new global::Google.Protobuf.TestProtos.Proto2.TestParsingMerge.Types.OptionalGroup();
+            }
+            input.ReadGroup(OptionalGroup);
+            break;
+          }
+          case 163: {
+            repeatedGroup_.AddEntriesFrom(input, _repeated_repeatedGroup_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -20615,6 +23344,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestParsingMerge, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -20649,7 +23379,11 @@
       /// Repeated fields in RepeatedFieldsGenerator are expected to be merged into
       /// the corresponding required/optional fields in TestParsingMerge.
       /// </summary>
-      public sealed partial class RepeatedFieldsGenerator : pb::IMessage<RepeatedFieldsGenerator>, pb::IBufferMessage {
+      public sealed partial class RepeatedFieldsGenerator : pb::IMessage<RepeatedFieldsGenerator>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<RepeatedFieldsGenerator> _parser = new pb::MessageParser<RepeatedFieldsGenerator>(() => new RepeatedFieldsGenerator());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -20850,9 +23584,49 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 10: {
+                field1_.AddEntriesFrom(input, _repeated_field1_codec);
+                break;
+              }
+              case 18: {
+                field2_.AddEntriesFrom(input, _repeated_field2_codec);
+                break;
+              }
+              case 26: {
+                field3_.AddEntriesFrom(input, _repeated_field3_codec);
+                break;
+              }
+              case 83: {
+                group1_.AddEntriesFrom(input, _repeated_group1_codec);
+                break;
+              }
+              case 163: {
+                group2_.AddEntriesFrom(input, _repeated_group2_codec);
+                break;
+              }
+              case 8002: {
+                ext1_.AddEntriesFrom(input, _repeated_ext1_codec);
+                break;
+              }
+              case 8010: {
+                ext2_.AddEntriesFrom(input, _repeated_ext2_codec);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -20892,12 +23666,17 @@
             }
           }
         }
+        #endif
 
         #region Nested types
         /// <summary>Container for nested types declared in the RepeatedFieldsGenerator message type.</summary>
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public static partial class Types {
-          public sealed partial class Group1 : pb::IMessage<Group1>, pb::IBufferMessage {
+          public sealed partial class Group1 : pb::IMessage<Group1>
+          #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+              , pb::IBufferMessage
+          #endif
+          {
             private static readonly pb::MessageParser<Group1> _parser = new pb::MessageParser<Group1>(() => new Group1());
             private pb::UnknownFieldSet _unknownFields;
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -21013,9 +23792,30 @@
 
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
             public void MergeFrom(pb::CodedInputStream input) {
+            #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
               input.ReadRawMessage(this);
+            #else
+              uint tag;
+              while ((tag = input.ReadTag()) != 0) {
+                switch(tag) {
+                  case 84:
+                    return;
+                  default:
+                    _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                    break;
+                  case 90: {
+                    if (field1_ == null) {
+                      Field1 = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+                    }
+                    input.ReadMessage(Field1);
+                    break;
+                  }
+                }
+              }
+            #endif
             }
 
+            #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
             void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
               uint tag;
@@ -21036,10 +23836,15 @@
                 }
               }
             }
+            #endif
 
           }
 
-          public sealed partial class Group2 : pb::IMessage<Group2>, pb::IBufferMessage {
+          public sealed partial class Group2 : pb::IMessage<Group2>
+          #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+              , pb::IBufferMessage
+          #endif
+          {
             private static readonly pb::MessageParser<Group2> _parser = new pb::MessageParser<Group2>(() => new Group2());
             private pb::UnknownFieldSet _unknownFields;
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -21155,9 +23960,30 @@
 
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
             public void MergeFrom(pb::CodedInputStream input) {
+            #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
               input.ReadRawMessage(this);
+            #else
+              uint tag;
+              while ((tag = input.ReadTag()) != 0) {
+                switch(tag) {
+                  case 164:
+                    return;
+                  default:
+                    _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                    break;
+                  case 170: {
+                    if (field1_ == null) {
+                      Field1 = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+                    }
+                    input.ReadMessage(Field1);
+                    break;
+                  }
+                }
+              }
+            #endif
             }
 
+            #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
             void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
               uint tag;
@@ -21178,6 +24004,7 @@
                 }
               }
             }
+            #endif
 
           }
 
@@ -21186,7 +24013,11 @@
 
       }
 
-      public sealed partial class OptionalGroup : pb::IMessage<OptionalGroup>, pb::IBufferMessage {
+      public sealed partial class OptionalGroup : pb::IMessage<OptionalGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<OptionalGroup> _parser = new pb::MessageParser<OptionalGroup>(() => new OptionalGroup());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -21302,9 +24133,30 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 84:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 90: {
+                if (optionalGroupAllTypes_ == null) {
+                  OptionalGroupAllTypes = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+                }
+                input.ReadMessage(OptionalGroupAllTypes);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -21325,10 +24177,15 @@
             }
           }
         }
+        #endif
 
       }
 
-      public sealed partial class RepeatedGroup : pb::IMessage<RepeatedGroup>, pb::IBufferMessage {
+      public sealed partial class RepeatedGroup : pb::IMessage<RepeatedGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<RepeatedGroup> _parser = new pb::MessageParser<RepeatedGroup>(() => new RepeatedGroup());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -21444,9 +24301,30 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 164:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 170: {
+                if (repeatedGroupAllTypes_ == null) {
+                  RepeatedGroupAllTypes = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+                }
+                input.ReadMessage(RepeatedGroupAllTypes);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -21467,6 +24345,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -21486,7 +24365,11 @@
 
   }
 
-  public sealed partial class TestCommentInjectionMessage : pb::IMessage<TestCommentInjectionMessage>, pb::IBufferMessage {
+  public sealed partial class TestCommentInjectionMessage : pb::IMessage<TestCommentInjectionMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestCommentInjectionMessage> _parser = new pb::MessageParser<TestCommentInjectionMessage>(() => new TestCommentInjectionMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -21614,9 +24497,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            A = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -21632,13 +24531,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test that RPC services work.
   /// </summary>
-  public sealed partial class FooRequest : pb::IMessage<FooRequest>, pb::IBufferMessage {
+  public sealed partial class FooRequest : pb::IMessage<FooRequest>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FooRequest> _parser = new pb::MessageParser<FooRequest>(() => new FooRequest());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -21727,9 +24631,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -21741,10 +24657,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class FooResponse : pb::IMessage<FooResponse>, pb::IBufferMessage {
+  public sealed partial class FooResponse : pb::IMessage<FooResponse>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FooResponse> _parser = new pb::MessageParser<FooResponse>(() => new FooResponse());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -21833,9 +24754,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -21847,10 +24780,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class FooClientMessage : pb::IMessage<FooClientMessage>, pb::IBufferMessage {
+  public sealed partial class FooClientMessage : pb::IMessage<FooClientMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FooClientMessage> _parser = new pb::MessageParser<FooClientMessage>(() => new FooClientMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -21939,9 +24877,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -21953,10 +24903,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class FooServerMessage : pb::IMessage<FooServerMessage>, pb::IBufferMessage {
+  public sealed partial class FooServerMessage : pb::IMessage<FooServerMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FooServerMessage> _parser = new pb::MessageParser<FooServerMessage>(() => new FooServerMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -22045,9 +25000,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -22059,10 +25026,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class BarRequest : pb::IMessage<BarRequest>, pb::IBufferMessage {
+  public sealed partial class BarRequest : pb::IMessage<BarRequest>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<BarRequest> _parser = new pb::MessageParser<BarRequest>(() => new BarRequest());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -22151,9 +25123,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -22165,10 +25149,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class BarResponse : pb::IMessage<BarResponse>, pb::IBufferMessage {
+  public sealed partial class BarResponse : pb::IMessage<BarResponse>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<BarResponse> _parser = new pb::MessageParser<BarResponse>(() => new BarResponse());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -22257,9 +25246,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -22271,10 +25272,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestJsonName : pb::IMessage<TestJsonName>, pb::IBufferMessage {
+  public sealed partial class TestJsonName : pb::IMessage<TestJsonName>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestJsonName> _parser = new pb::MessageParser<TestJsonName>(() => new TestJsonName());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -22587,9 +25593,45 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            FieldName1 = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            FieldName2 = input.ReadInt32();
+            break;
+          }
+          case 24: {
+            FieldName3 = input.ReadInt32();
+            break;
+          }
+          case 32: {
+            FieldName4 = input.ReadInt32();
+            break;
+          }
+          case 40: {
+            FIELDNAME5 = input.ReadInt32();
+            break;
+          }
+          case 48: {
+            FieldName6 = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -22625,10 +25667,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestHugeFieldNumbers : pb::IExtendableMessage<TestHugeFieldNumbers>, pb::IBufferMessage {
+  public sealed partial class TestHugeFieldNumbers : pb::IExtendableMessage<TestHugeFieldNumbers>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestHugeFieldNumbers> _parser = new pb::MessageParser<TestHugeFieldNumbers>(() => new TestHugeFieldNumbers());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestHugeFieldNumbers> _extensions;
@@ -23203,9 +26250,92 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 4294960000: {
+            OptionalInt32 = input.ReadInt32();
+            break;
+          }
+          case 4294960008: {
+            Fixed32 = input.ReadInt32();
+            break;
+          }
+          case 4294960018:
+          case 4294960016: {
+            repeatedInt32_.AddEntriesFrom(input, _repeated_repeatedInt32_codec);
+            break;
+          }
+          case 4294960026:
+          case 4294960024: {
+            packedInt32_.AddEntriesFrom(input, _repeated_packedInt32_codec);
+            break;
+          }
+          case 4294960032: {
+            OptionalEnum = (global::Google.Protobuf.TestProtos.Proto2.ForeignEnum) input.ReadEnum();
+            break;
+          }
+          case 4294960042: {
+            OptionalString = input.ReadString();
+            break;
+          }
+          case 4294960050: {
+            OptionalBytes = input.ReadBytes();
+            break;
+          }
+          case 4294960058: {
+            if (optionalMessage_ == null) {
+              OptionalMessage = new global::Google.Protobuf.TestProtos.Proto2.ForeignMessage();
+            }
+            input.ReadMessage(OptionalMessage);
+            break;
+          }
+          case 4294960067: {
+            if (!HasOptionalGroup) {
+              OptionalGroup = new global::Google.Protobuf.TestProtos.Proto2.TestHugeFieldNumbers.Types.OptionalGroup();
+            }
+            input.ReadGroup(OptionalGroup);
+            break;
+          }
+          case 4294960082: {
+            stringStringMap_.AddEntriesFrom(input, _map_stringStringMap_codec);
+            break;
+          }
+          case 4294960088: {
+            OneofUint32 = input.ReadUInt32();
+            break;
+          }
+          case 4294960098: {
+            global::Google.Protobuf.TestProtos.Proto2.TestAllTypes subBuilder = new global::Google.Protobuf.TestProtos.Proto2.TestAllTypes();
+            if (oneofFieldCase_ == OneofFieldOneofCase.OneofTestAllTypes) {
+              subBuilder.MergeFrom(OneofTestAllTypes);
+            }
+            input.ReadMessage(subBuilder);
+            OneofTestAllTypes = subBuilder;
+            break;
+          }
+          case 4294960106: {
+            OneofString = input.ReadString();
+            break;
+          }
+          case 4294960114: {
+            OneofBytes = input.ReadBytes();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -23288,6 +26418,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestHugeFieldNumbers, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -23315,7 +26446,11 @@
     /// <summary>Container for nested types declared in the TestHugeFieldNumbers message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class OptionalGroup : pb::IMessage<OptionalGroup>, pb::IBufferMessage {
+      public sealed partial class OptionalGroup : pb::IMessage<OptionalGroup>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<OptionalGroup> _parser = new pb::MessageParser<OptionalGroup>(() => new OptionalGroup());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -23443,9 +26578,27 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              case 4294960068:
+                return;
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 4294960072: {
+                GroupA = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -23463,6 +26616,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -23471,7 +26625,11 @@
 
   }
 
-  public sealed partial class TestExtensionInsideTable : pb::IExtendableMessage<TestExtensionInsideTable>, pb::IBufferMessage {
+  public sealed partial class TestExtensionInsideTable : pb::IExtendableMessage<TestExtensionInsideTable>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestExtensionInsideTable> _parser = new pb::MessageParser<TestExtensionInsideTable>(() => new TestExtensionInsideTable());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<TestExtensionInsideTable> _extensions;
@@ -23911,9 +27069,59 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 8: {
+            Field1 = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            Field2 = input.ReadInt32();
+            break;
+          }
+          case 24: {
+            Field3 = input.ReadInt32();
+            break;
+          }
+          case 32: {
+            Field4 = input.ReadInt32();
+            break;
+          }
+          case 48: {
+            Field6 = input.ReadInt32();
+            break;
+          }
+          case 56: {
+            Field7 = input.ReadInt32();
+            break;
+          }
+          case 64: {
+            Field8 = input.ReadInt32();
+            break;
+          }
+          case 72: {
+            Field9 = input.ReadInt32();
+            break;
+          }
+          case 80: {
+            Field10 = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -23963,6 +27171,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<TestExtensionInsideTable, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestCustomOptionsProto3.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestCustomOptionsProto3.cs
index 818748b..26455da 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestCustomOptionsProto3.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestCustomOptionsProto3.cs
@@ -257,7 +257,11 @@
   /// A test message with custom options at all possible locations (and also some
   /// regular options, to make sure they interact nicely).
   /// </summary>
-  public sealed partial class TestMessageWithCustomOptions : pb::IMessage<TestMessageWithCustomOptions>, pb::IBufferMessage {
+  public sealed partial class TestMessageWithCustomOptions : pb::IMessage<TestMessageWithCustomOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestMessageWithCustomOptions> _parser = new pb::MessageParser<TestMessageWithCustomOptions>(() => new TestMessageWithCustomOptions());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -422,9 +426,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Field1 = input.ReadString();
+            break;
+          }
+          case 16: {
+            OneofField = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -444,6 +468,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestMessageWithCustomOptions message type.</summary>
@@ -464,7 +489,11 @@
   /// A test RPC service with custom options at all possible locations (and also
   /// some regular options, to make sure they interact nicely).
   /// </summary>
-  public sealed partial class CustomOptionFooRequest : pb::IMessage<CustomOptionFooRequest>, pb::IBufferMessage {
+  public sealed partial class CustomOptionFooRequest : pb::IMessage<CustomOptionFooRequest>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<CustomOptionFooRequest> _parser = new pb::MessageParser<CustomOptionFooRequest>(() => new CustomOptionFooRequest());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -553,9 +582,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -567,10 +608,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class CustomOptionFooResponse : pb::IMessage<CustomOptionFooResponse>, pb::IBufferMessage {
+  public sealed partial class CustomOptionFooResponse : pb::IMessage<CustomOptionFooResponse>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<CustomOptionFooResponse> _parser = new pb::MessageParser<CustomOptionFooResponse>(() => new CustomOptionFooResponse());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -659,9 +705,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -673,10 +731,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class CustomOptionFooClientMessage : pb::IMessage<CustomOptionFooClientMessage>, pb::IBufferMessage {
+  public sealed partial class CustomOptionFooClientMessage : pb::IMessage<CustomOptionFooClientMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<CustomOptionFooClientMessage> _parser = new pb::MessageParser<CustomOptionFooClientMessage>(() => new CustomOptionFooClientMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -765,9 +828,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -779,10 +854,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class CustomOptionFooServerMessage : pb::IMessage<CustomOptionFooServerMessage>, pb::IBufferMessage {
+  public sealed partial class CustomOptionFooServerMessage : pb::IMessage<CustomOptionFooServerMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<CustomOptionFooServerMessage> _parser = new pb::MessageParser<CustomOptionFooServerMessage>(() => new CustomOptionFooServerMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -871,9 +951,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -885,10 +977,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class DummyMessageContainingEnum : pb::IMessage<DummyMessageContainingEnum>, pb::IBufferMessage {
+  public sealed partial class DummyMessageContainingEnum : pb::IMessage<DummyMessageContainingEnum>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<DummyMessageContainingEnum> _parser = new pb::MessageParser<DummyMessageContainingEnum>(() => new DummyMessageContainingEnum());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -977,9 +1074,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -991,6 +1100,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the DummyMessageContainingEnum message type.</summary>
@@ -1007,7 +1117,11 @@
 
   }
 
-  public sealed partial class DummyMessageInvalidAsOptionType : pb::IMessage<DummyMessageInvalidAsOptionType>, pb::IBufferMessage {
+  public sealed partial class DummyMessageInvalidAsOptionType : pb::IMessage<DummyMessageInvalidAsOptionType>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<DummyMessageInvalidAsOptionType> _parser = new pb::MessageParser<DummyMessageInvalidAsOptionType>(() => new DummyMessageInvalidAsOptionType());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1096,9 +1210,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1110,10 +1236,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class CustomOptionMinIntegerValues : pb::IMessage<CustomOptionMinIntegerValues>, pb::IBufferMessage {
+  public sealed partial class CustomOptionMinIntegerValues : pb::IMessage<CustomOptionMinIntegerValues>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<CustomOptionMinIntegerValues> _parser = new pb::MessageParser<CustomOptionMinIntegerValues>(() => new CustomOptionMinIntegerValues());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1202,9 +1333,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1216,10 +1359,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class CustomOptionMaxIntegerValues : pb::IMessage<CustomOptionMaxIntegerValues>, pb::IBufferMessage {
+  public sealed partial class CustomOptionMaxIntegerValues : pb::IMessage<CustomOptionMaxIntegerValues>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<CustomOptionMaxIntegerValues> _parser = new pb::MessageParser<CustomOptionMaxIntegerValues>(() => new CustomOptionMaxIntegerValues());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1308,9 +1456,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1322,10 +1482,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class CustomOptionOtherValues : pb::IMessage<CustomOptionOtherValues>, pb::IBufferMessage {
+  public sealed partial class CustomOptionOtherValues : pb::IMessage<CustomOptionOtherValues>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<CustomOptionOtherValues> _parser = new pb::MessageParser<CustomOptionOtherValues>(() => new CustomOptionOtherValues());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1414,9 +1579,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1428,10 +1605,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class SettingRealsFromPositiveInts : pb::IMessage<SettingRealsFromPositiveInts>, pb::IBufferMessage {
+  public sealed partial class SettingRealsFromPositiveInts : pb::IMessage<SettingRealsFromPositiveInts>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<SettingRealsFromPositiveInts> _parser = new pb::MessageParser<SettingRealsFromPositiveInts>(() => new SettingRealsFromPositiveInts());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1520,9 +1702,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1534,10 +1728,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class SettingRealsFromNegativeInts : pb::IMessage<SettingRealsFromNegativeInts>, pb::IBufferMessage {
+  public sealed partial class SettingRealsFromNegativeInts : pb::IMessage<SettingRealsFromNegativeInts>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<SettingRealsFromNegativeInts> _parser = new pb::MessageParser<SettingRealsFromNegativeInts>(() => new SettingRealsFromNegativeInts());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1626,9 +1825,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1640,10 +1851,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class ComplexOptionType1 : pb::IMessage<ComplexOptionType1>, pb::IBufferMessage {
+  public sealed partial class ComplexOptionType1 : pb::IMessage<ComplexOptionType1>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ComplexOptionType1> _parser = new pb::MessageParser<ComplexOptionType1>(() => new ComplexOptionType1());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1820,9 +2036,38 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Foo = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            Foo2 = input.ReadInt32();
+            break;
+          }
+          case 24: {
+            Foo3 = input.ReadInt32();
+            break;
+          }
+          case 34:
+          case 32: {
+            foo4_.AddEntriesFrom(input, _repeated_foo4_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1851,10 +2096,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class ComplexOptionType2 : pb::IMessage<ComplexOptionType2>, pb::IBufferMessage {
+  public sealed partial class ComplexOptionType2 : pb::IMessage<ComplexOptionType2>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ComplexOptionType2> _parser = new pb::MessageParser<ComplexOptionType2>(() => new ComplexOptionType2());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2037,9 +2287,43 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (bar_ == null) {
+              Bar = new global::UnitTest.Issues.TestProtos.ComplexOptionType1();
+            }
+            input.ReadMessage(Bar);
+            break;
+          }
+          case 16: {
+            Baz = input.ReadInt32();
+            break;
+          }
+          case 26: {
+            if (fred_ == null) {
+              Fred = new global::UnitTest.Issues.TestProtos.ComplexOptionType2.Types.ComplexOptionType4();
+            }
+            input.ReadMessage(Fred);
+            break;
+          }
+          case 34: {
+            barney_.AddEntriesFrom(input, _repeated_barney_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2073,12 +2357,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the ComplexOptionType2 message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class ComplexOptionType4 : pb::IMessage<ComplexOptionType4>, pb::IBufferMessage {
+      public sealed partial class ComplexOptionType4 : pb::IMessage<ComplexOptionType4>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<ComplexOptionType4> _parser = new pb::MessageParser<ComplexOptionType4>(() => new ComplexOptionType4());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2191,9 +2480,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                Waldo = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -2209,6 +2514,7 @@
             }
           }
         }
+        #endif
 
         #region Extensions
         /// <summary>Container for extensions for other messages declared in the ComplexOptionType4 message type.</summary>
@@ -2226,7 +2532,11 @@
 
   }
 
-  public sealed partial class ComplexOptionType3 : pb::IMessage<ComplexOptionType3>, pb::IBufferMessage {
+  public sealed partial class ComplexOptionType3 : pb::IMessage<ComplexOptionType3>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ComplexOptionType3> _parser = new pb::MessageParser<ComplexOptionType3>(() => new ComplexOptionType3());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2339,9 +2649,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Qux = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2357,13 +2683,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Note that we try various different ways of naming the same extension.
   /// </summary>
-  public sealed partial class VariousComplexOptions : pb::IMessage<VariousComplexOptions>, pb::IBufferMessage {
+  public sealed partial class VariousComplexOptions : pb::IMessage<VariousComplexOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<VariousComplexOptions> _parser = new pb::MessageParser<VariousComplexOptions>(() => new VariousComplexOptions());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2452,9 +2783,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2466,13 +2809,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// A helper type used to test aggregate option parsing
   /// </summary>
-  public sealed partial class Aggregate : pb::IMessage<Aggregate>, pb::IBufferMessage {
+  public sealed partial class Aggregate : pb::IMessage<Aggregate>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Aggregate> _parser = new pb::MessageParser<Aggregate>(() => new Aggregate());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2639,9 +2987,36 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            I = input.ReadInt32();
+            break;
+          }
+          case 18: {
+            S = input.ReadString();
+            break;
+          }
+          case 26: {
+            if (sub_ == null) {
+              Sub = new global::UnitTest.Issues.TestProtos.Aggregate();
+            }
+            input.ReadMessage(Sub);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2668,10 +3043,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class AggregateMessage : pb::IMessage<AggregateMessage>, pb::IBufferMessage {
+  public sealed partial class AggregateMessage : pb::IMessage<AggregateMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<AggregateMessage> _parser = new pb::MessageParser<AggregateMessage>(() => new AggregateMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2784,9 +3164,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Fieldname = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2802,13 +3198,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test custom options for nested type.
   /// </summary>
-  public sealed partial class NestedOptionType : pb::IMessage<NestedOptionType>, pb::IBufferMessage {
+  public sealed partial class NestedOptionType : pb::IMessage<NestedOptionType>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<NestedOptionType> _parser = new pb::MessageParser<NestedOptionType>(() => new NestedOptionType());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2897,9 +3298,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2911,6 +3324,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the NestedOptionType message type.</summary>
@@ -2921,7 +3335,11 @@
         [pbr::OriginalName("NESTED_ENUM_VALUE")] Value = 1,
       }
 
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3034,9 +3452,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                NestedField = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -3052,6 +3486,7 @@
             }
           }
         }
+        #endif
 
       }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImport.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImport.cs
index 1cddcd8..6ac9f11 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImport.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImport.cs
@@ -59,7 +59,11 @@
   #endregion
 
   #region Messages
-  public sealed partial class ImportMessage : pb::IMessage<ImportMessage>, pb::IBufferMessage {
+  public sealed partial class ImportMessage : pb::IMessage<ImportMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ImportMessage> _parser = new pb::MessageParser<ImportMessage>(() => new ImportMessage());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -187,9 +191,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            D = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -205,6 +225,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportProto3.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportProto3.cs
index bcd27bf..99575b1 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportProto3.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportProto3.cs
@@ -50,7 +50,11 @@
   #endregion
 
   #region Messages
-  public sealed partial class ImportMessage : pb::IMessage<ImportMessage>, pb::IBufferMessage {
+  public sealed partial class ImportMessage : pb::IMessage<ImportMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ImportMessage> _parser = new pb::MessageParser<ImportMessage>(() => new ImportMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -163,9 +167,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            D = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -181,6 +201,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportPublic.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportPublic.cs
index 6b35c10..9bdcf1d 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportPublic.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportPublic.cs
@@ -37,7 +37,11 @@
 
   }
   #region Messages
-  public sealed partial class PublicImportMessage : pb::IMessage<PublicImportMessage>, pb::IBufferMessage {
+  public sealed partial class PublicImportMessage : pb::IMessage<PublicImportMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<PublicImportMessage> _parser = new pb::MessageParser<PublicImportMessage>(() => new PublicImportMessage());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -165,9 +169,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            E = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -183,6 +203,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportPublicProto3.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportPublicProto3.cs
index 664c666..dba9165 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportPublicProto3.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestImportPublicProto3.cs
@@ -38,7 +38,11 @@
 
   }
   #region Messages
-  public sealed partial class PublicImportMessage : pb::IMessage<PublicImportMessage>, pb::IBufferMessage {
+  public sealed partial class PublicImportMessage : pb::IMessage<PublicImportMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<PublicImportMessage> _parser = new pb::MessageParser<PublicImportMessage>(() => new PublicImportMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -151,9 +155,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            E = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -169,6 +189,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssue6936B.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssue6936B.cs
index bede87a..660dbbd 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssue6936B.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssue6936B.cs
@@ -37,7 +37,11 @@
 
   }
   #region Messages
-  public sealed partial class Foo : pb::IMessage<Foo>, pb::IBufferMessage {
+  public sealed partial class Foo : pb::IMessage<Foo>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Foo> _parser = new pb::MessageParser<Foo>(() => new Foo());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -126,9 +130,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -140,6 +156,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssue6936C.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssue6936C.cs
index e86780f..b7498d6 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssue6936C.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssue6936C.cs
@@ -39,7 +39,11 @@
 
   }
   #region Messages
-  public sealed partial class Bar : pb::IMessage<Bar>, pb::IBufferMessage {
+  public sealed partial class Bar : pb::IMessage<Bar>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Bar> _parser = new pb::MessageParser<Bar>(() => new Bar());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -155,9 +159,28 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (foo_ == null) {
+              Foo = new global::UnitTest.Issues.TestProtos.Foo();
+            }
+            input.ReadMessage(Foo);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -176,6 +199,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssues.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssues.cs
index 68884e1..f5c46a9 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssues.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssues.cs
@@ -88,7 +88,11 @@
   /// Issue 307: when generating doubly-nested types, any references
   /// should be of the form A.Types.B.Types.C.
   /// </summary>
-  public sealed partial class Issue307 : pb::IMessage<Issue307>, pb::IBufferMessage {
+  public sealed partial class Issue307 : pb::IMessage<Issue307>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Issue307> _parser = new pb::MessageParser<Issue307>(() => new Issue307());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -177,9 +181,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -191,12 +207,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the Issue307 message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class NestedOnce : pb::IMessage<NestedOnce>, pb::IBufferMessage {
+      public sealed partial class NestedOnce : pb::IMessage<NestedOnce>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedOnce> _parser = new pb::MessageParser<NestedOnce>(() => new NestedOnce());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -285,9 +306,21 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -299,12 +332,17 @@
             }
           }
         }
+        #endif
 
         #region Nested types
         /// <summary>Container for nested types declared in the NestedOnce message type.</summary>
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public static partial class Types {
-          public sealed partial class NestedTwice : pb::IMessage<NestedTwice>, pb::IBufferMessage {
+          public sealed partial class NestedTwice : pb::IMessage<NestedTwice>
+          #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+              , pb::IBufferMessage
+          #endif
+          {
             private static readonly pb::MessageParser<NestedTwice> _parser = new pb::MessageParser<NestedTwice>(() => new NestedTwice());
             private pb::UnknownFieldSet _unknownFields;
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -393,9 +431,21 @@
 
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
             public void MergeFrom(pb::CodedInputStream input) {
+            #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
               input.ReadRawMessage(this);
+            #else
+              uint tag;
+              while ((tag = input.ReadTag()) != 0) {
+                switch(tag) {
+                  default:
+                    _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                    break;
+                }
+              }
+            #endif
             }
 
+            #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
             void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
               uint tag;
@@ -407,6 +457,7 @@
                 }
               }
             }
+            #endif
 
           }
 
@@ -420,7 +471,11 @@
 
   }
 
-  public sealed partial class NegativeEnumMessage : pb::IMessage<NegativeEnumMessage>, pb::IBufferMessage {
+  public sealed partial class NegativeEnumMessage : pb::IMessage<NegativeEnumMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<NegativeEnumMessage> _parser = new pb::MessageParser<NegativeEnumMessage>(() => new NegativeEnumMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -565,9 +620,35 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Value = (global::UnitTest.Issues.TestProtos.NegativeEnum) input.ReadEnum();
+            break;
+          }
+          case 18:
+          case 16: {
+            values_.AddEntriesFrom(input, _repeated_values_codec);
+            break;
+          }
+          case 26:
+          case 24: {
+            packedValues_.AddEntriesFrom(input, _repeated_packedValues_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -593,10 +674,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class DeprecatedChild : pb::IMessage<DeprecatedChild>, pb::IBufferMessage {
+  public sealed partial class DeprecatedChild : pb::IMessage<DeprecatedChild>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<DeprecatedChild> _parser = new pb::MessageParser<DeprecatedChild>(() => new DeprecatedChild());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -685,9 +771,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -699,10 +797,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class DeprecatedFieldsMessage : pb::IMessage<DeprecatedFieldsMessage>, pb::IBufferMessage {
+  public sealed partial class DeprecatedFieldsMessage : pb::IMessage<DeprecatedFieldsMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<DeprecatedFieldsMessage> _parser = new pb::MessageParser<DeprecatedFieldsMessage>(() => new DeprecatedFieldsMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -920,9 +1023,50 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            PrimitiveValue = input.ReadInt32();
+            break;
+          }
+          case 18:
+          case 16: {
+            primitiveArray_.AddEntriesFrom(input, _repeated_primitiveArray_codec);
+            break;
+          }
+          case 26: {
+            if (messageValue_ == null) {
+              MessageValue = new global::UnitTest.Issues.TestProtos.DeprecatedChild();
+            }
+            input.ReadMessage(MessageValue);
+            break;
+          }
+          case 34: {
+            messageArray_.AddEntriesFrom(input, _repeated_messageArray_codec);
+            break;
+          }
+          case 40: {
+            EnumValue = (global::UnitTest.Issues.TestProtos.DeprecatedEnum) input.ReadEnum();
+            break;
+          }
+          case 50:
+          case 48: {
+            enumArray_.AddEntriesFrom(input, _repeated_enumArray_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -963,13 +1107,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Issue 45: http://code.google.com/p/protobuf-csharp-port/issues/detail?id=45
   /// </summary>
-  public sealed partial class ItemField : pb::IMessage<ItemField>, pb::IBufferMessage {
+  public sealed partial class ItemField : pb::IMessage<ItemField>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ItemField> _parser = new pb::MessageParser<ItemField>(() => new ItemField());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1082,9 +1231,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Item = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1100,10 +1265,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class ReservedNames : pb::IMessage<ReservedNames>, pb::IBufferMessage {
+  public sealed partial class ReservedNames : pb::IMessage<ReservedNames>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ReservedNames> _parser = new pb::MessageParser<ReservedNames>(() => new ReservedNames());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1240,9 +1410,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Types_ = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            Descriptor_ = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1262,6 +1452,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the ReservedNames message type.</summary>
@@ -1270,7 +1461,11 @@
       /// <summary>
       /// Force a nested type called Types
       /// </summary>
-      public sealed partial class SomeNestedType : pb::IMessage<SomeNestedType>, pb::IBufferMessage {
+      public sealed partial class SomeNestedType : pb::IMessage<SomeNestedType>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<SomeNestedType> _parser = new pb::MessageParser<SomeNestedType>(() => new SomeNestedType());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1359,9 +1554,21 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -1373,6 +1580,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -1393,7 +1601,11 @@
   /// Alternatively, consider just adding this to
   /// unittest_proto3.proto if multiple platforms want it.
   /// </summary>
-  public sealed partial class TestJsonFieldOrdering : pb::IMessage<TestJsonFieldOrdering>, pb::IBufferMessage {
+  public sealed partial class TestJsonFieldOrdering : pb::IMessage<TestJsonFieldOrdering>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestJsonFieldOrdering> _parser = new pb::MessageParser<TestJsonFieldOrdering>(() => new TestJsonFieldOrdering());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1688,9 +1900,45 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            PlainString = input.ReadString();
+            break;
+          }
+          case 18: {
+            O1String = input.ReadString();
+            break;
+          }
+          case 26: {
+            O2String = input.ReadString();
+            break;
+          }
+          case 32: {
+            PlainInt32 = input.ReadInt32();
+            break;
+          }
+          case 40: {
+            O1Int32 = input.ReadInt32();
+            break;
+          }
+          case 48: {
+            O2Int32 = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1726,10 +1974,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestJsonName : pb::IMessage<TestJsonName>, pb::IBufferMessage {
+  public sealed partial class TestJsonName : pb::IMessage<TestJsonName>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestJsonName> _parser = new pb::MessageParser<TestJsonName>(() => new TestJsonName());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1893,9 +2146,33 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            Description = input.ReadString();
+            break;
+          }
+          case 26: {
+            Guid = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1919,6 +2196,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -1927,7 +2205,11 @@
   /// oneof case, which is itself a message type, the submessages should
   /// be merged.
   /// </summary>
-  public sealed partial class OneofMerging : pb::IMessage<OneofMerging>, pb::IBufferMessage {
+  public sealed partial class OneofMerging : pb::IMessage<OneofMerging>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<OneofMerging> _parser = new pb::MessageParser<OneofMerging>(() => new OneofMerging());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2098,9 +2380,34 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Text = input.ReadString();
+            break;
+          }
+          case 18: {
+            global::UnitTest.Issues.TestProtos.OneofMerging.Types.Nested subBuilder = new global::UnitTest.Issues.TestProtos.OneofMerging.Types.Nested();
+            if (valueCase_ == ValueOneofCase.Nested) {
+              subBuilder.MergeFrom(Nested);
+            }
+            input.ReadMessage(subBuilder);
+            Nested = subBuilder;
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2125,12 +2432,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the OneofMerging message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class Nested : pb::IMessage<Nested>, pb::IBufferMessage {
+      public sealed partial class Nested : pb::IMessage<Nested>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<Nested> _parser = new pb::MessageParser<Nested>(() => new Nested());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2267,9 +2579,29 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                X = input.ReadInt32();
+                break;
+              }
+              case 16: {
+                Y = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -2289,6 +2621,7 @@
             }
           }
         }
+        #endif
 
       }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestProto3.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestProto3.cs
index 5d0ea86..468e48b 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestProto3.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestProto3.cs
@@ -254,7 +254,11 @@
   /// This proto includes every type of field in both singular and repeated
   /// forms.
   /// </summary>
-  public sealed partial class TestAllTypes : pb::IMessage<TestAllTypes>, pb::IBufferMessage {
+  public sealed partial class TestAllTypes : pb::IMessage<TestAllTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestAllTypes> _parser = new pb::MessageParser<TestAllTypes>(() => new TestAllTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1383,9 +1387,246 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            SingleInt32 = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            SingleInt64 = input.ReadInt64();
+            break;
+          }
+          case 24: {
+            SingleUint32 = input.ReadUInt32();
+            break;
+          }
+          case 32: {
+            SingleUint64 = input.ReadUInt64();
+            break;
+          }
+          case 40: {
+            SingleSint32 = input.ReadSInt32();
+            break;
+          }
+          case 48: {
+            SingleSint64 = input.ReadSInt64();
+            break;
+          }
+          case 61: {
+            SingleFixed32 = input.ReadFixed32();
+            break;
+          }
+          case 65: {
+            SingleFixed64 = input.ReadFixed64();
+            break;
+          }
+          case 77: {
+            SingleSfixed32 = input.ReadSFixed32();
+            break;
+          }
+          case 81: {
+            SingleSfixed64 = input.ReadSFixed64();
+            break;
+          }
+          case 93: {
+            SingleFloat = input.ReadFloat();
+            break;
+          }
+          case 97: {
+            SingleDouble = input.ReadDouble();
+            break;
+          }
+          case 104: {
+            SingleBool = input.ReadBool();
+            break;
+          }
+          case 114: {
+            SingleString = input.ReadString();
+            break;
+          }
+          case 122: {
+            SingleBytes = input.ReadBytes();
+            break;
+          }
+          case 146: {
+            if (singleNestedMessage_ == null) {
+              SingleNestedMessage = new global::Google.Protobuf.TestProtos.TestAllTypes.Types.NestedMessage();
+            }
+            input.ReadMessage(SingleNestedMessage);
+            break;
+          }
+          case 154: {
+            if (singleForeignMessage_ == null) {
+              SingleForeignMessage = new global::Google.Protobuf.TestProtos.ForeignMessage();
+            }
+            input.ReadMessage(SingleForeignMessage);
+            break;
+          }
+          case 162: {
+            if (singleImportMessage_ == null) {
+              SingleImportMessage = new global::Google.Protobuf.TestProtos.ImportMessage();
+            }
+            input.ReadMessage(SingleImportMessage);
+            break;
+          }
+          case 168: {
+            SingleNestedEnum = (global::Google.Protobuf.TestProtos.TestAllTypes.Types.NestedEnum) input.ReadEnum();
+            break;
+          }
+          case 176: {
+            SingleForeignEnum = (global::Google.Protobuf.TestProtos.ForeignEnum) input.ReadEnum();
+            break;
+          }
+          case 184: {
+            SingleImportEnum = (global::Google.Protobuf.TestProtos.ImportEnum) input.ReadEnum();
+            break;
+          }
+          case 210: {
+            if (singlePublicImportMessage_ == null) {
+              SinglePublicImportMessage = new global::Google.Protobuf.TestProtos.PublicImportMessage();
+            }
+            input.ReadMessage(SinglePublicImportMessage);
+            break;
+          }
+          case 250:
+          case 248: {
+            repeatedInt32_.AddEntriesFrom(input, _repeated_repeatedInt32_codec);
+            break;
+          }
+          case 258:
+          case 256: {
+            repeatedInt64_.AddEntriesFrom(input, _repeated_repeatedInt64_codec);
+            break;
+          }
+          case 266:
+          case 264: {
+            repeatedUint32_.AddEntriesFrom(input, _repeated_repeatedUint32_codec);
+            break;
+          }
+          case 274:
+          case 272: {
+            repeatedUint64_.AddEntriesFrom(input, _repeated_repeatedUint64_codec);
+            break;
+          }
+          case 282:
+          case 280: {
+            repeatedSint32_.AddEntriesFrom(input, _repeated_repeatedSint32_codec);
+            break;
+          }
+          case 290:
+          case 288: {
+            repeatedSint64_.AddEntriesFrom(input, _repeated_repeatedSint64_codec);
+            break;
+          }
+          case 298:
+          case 301: {
+            repeatedFixed32_.AddEntriesFrom(input, _repeated_repeatedFixed32_codec);
+            break;
+          }
+          case 306:
+          case 305: {
+            repeatedFixed64_.AddEntriesFrom(input, _repeated_repeatedFixed64_codec);
+            break;
+          }
+          case 314:
+          case 317: {
+            repeatedSfixed32_.AddEntriesFrom(input, _repeated_repeatedSfixed32_codec);
+            break;
+          }
+          case 322:
+          case 321: {
+            repeatedSfixed64_.AddEntriesFrom(input, _repeated_repeatedSfixed64_codec);
+            break;
+          }
+          case 330:
+          case 333: {
+            repeatedFloat_.AddEntriesFrom(input, _repeated_repeatedFloat_codec);
+            break;
+          }
+          case 338:
+          case 337: {
+            repeatedDouble_.AddEntriesFrom(input, _repeated_repeatedDouble_codec);
+            break;
+          }
+          case 346:
+          case 344: {
+            repeatedBool_.AddEntriesFrom(input, _repeated_repeatedBool_codec);
+            break;
+          }
+          case 354: {
+            repeatedString_.AddEntriesFrom(input, _repeated_repeatedString_codec);
+            break;
+          }
+          case 362: {
+            repeatedBytes_.AddEntriesFrom(input, _repeated_repeatedBytes_codec);
+            break;
+          }
+          case 386: {
+            repeatedNestedMessage_.AddEntriesFrom(input, _repeated_repeatedNestedMessage_codec);
+            break;
+          }
+          case 394: {
+            repeatedForeignMessage_.AddEntriesFrom(input, _repeated_repeatedForeignMessage_codec);
+            break;
+          }
+          case 402: {
+            repeatedImportMessage_.AddEntriesFrom(input, _repeated_repeatedImportMessage_codec);
+            break;
+          }
+          case 410:
+          case 408: {
+            repeatedNestedEnum_.AddEntriesFrom(input, _repeated_repeatedNestedEnum_codec);
+            break;
+          }
+          case 418:
+          case 416: {
+            repeatedForeignEnum_.AddEntriesFrom(input, _repeated_repeatedForeignEnum_codec);
+            break;
+          }
+          case 426:
+          case 424: {
+            repeatedImportEnum_.AddEntriesFrom(input, _repeated_repeatedImportEnum_codec);
+            break;
+          }
+          case 434: {
+            repeatedPublicImportMessage_.AddEntriesFrom(input, _repeated_repeatedPublicImportMessage_codec);
+            break;
+          }
+          case 888: {
+            OneofUint32 = input.ReadUInt32();
+            break;
+          }
+          case 898: {
+            global::Google.Protobuf.TestProtos.TestAllTypes.Types.NestedMessage subBuilder = new global::Google.Protobuf.TestProtos.TestAllTypes.Types.NestedMessage();
+            if (oneofFieldCase_ == OneofFieldOneofCase.OneofNestedMessage) {
+              subBuilder.MergeFrom(OneofNestedMessage);
+            }
+            input.ReadMessage(subBuilder);
+            OneofNestedMessage = subBuilder;
+            break;
+          }
+          case 906: {
+            OneofString = input.ReadString();
+            break;
+          }
+          case 914: {
+            OneofBytes = input.ReadBytes();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1622,6 +1863,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestAllTypes message type.</summary>
@@ -1638,7 +1880,11 @@
         [pbr::OriginalName("NEG")] Neg = -1,
       }
 
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1756,9 +2002,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                Bb = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -1774,6 +2036,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -1785,7 +2048,11 @@
   /// <summary>
   /// This proto includes a recursively nested message.
   /// </summary>
-  public sealed partial class NestedTestAllTypes : pb::IMessage<NestedTestAllTypes>, pb::IBufferMessage {
+  public sealed partial class NestedTestAllTypes : pb::IMessage<NestedTestAllTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<NestedTestAllTypes> _parser = new pb::MessageParser<NestedTestAllTypes>(() => new NestedTestAllTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1944,9 +2211,39 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (child_ == null) {
+              Child = new global::Google.Protobuf.TestProtos.NestedTestAllTypes();
+            }
+            input.ReadMessage(Child);
+            break;
+          }
+          case 18: {
+            if (payload_ == null) {
+              Payload = new global::Google.Protobuf.TestProtos.TestAllTypes();
+            }
+            input.ReadMessage(Payload);
+            break;
+          }
+          case 26: {
+            repeatedChild_.AddEntriesFrom(input, _repeated_repeatedChild_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1976,10 +2273,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestDeprecatedFields : pb::IMessage<TestDeprecatedFields>, pb::IBufferMessage {
+  public sealed partial class TestDeprecatedFields : pb::IMessage<TestDeprecatedFields>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestDeprecatedFields> _parser = new pb::MessageParser<TestDeprecatedFields>(() => new TestDeprecatedFields());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2093,9 +2395,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            DeprecatedInt32 = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2111,6 +2429,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -2118,7 +2437,11 @@
   /// Define these after TestAllTypes to make sure the compiler can handle
   /// that.
   /// </summary>
-  public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage>, pb::IBufferMessage {
+  public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ForeignMessage> _parser = new pb::MessageParser<ForeignMessage>(() => new ForeignMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2231,9 +2554,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            C = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2249,10 +2588,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestReservedFields : pb::IMessage<TestReservedFields>, pb::IBufferMessage {
+  public sealed partial class TestReservedFields : pb::IMessage<TestReservedFields>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestReservedFields> _parser = new pb::MessageParser<TestReservedFields>(() => new TestReservedFields());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2341,9 +2685,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2355,13 +2711,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test that we can use NestedMessage from outside TestAllTypes.
   /// </summary>
-  public sealed partial class TestForeignNested : pb::IMessage<TestForeignNested>, pb::IBufferMessage {
+  public sealed partial class TestForeignNested : pb::IMessage<TestForeignNested>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestForeignNested> _parser = new pb::MessageParser<TestForeignNested>(() => new TestForeignNested());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2477,9 +2838,28 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (foreignNested_ == null) {
+              ForeignNested = new global::Google.Protobuf.TestProtos.TestAllTypes.Types.NestedMessage();
+            }
+            input.ReadMessage(ForeignNested);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2498,13 +2878,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test that really large tag numbers don't break anything.
   /// </summary>
-  public sealed partial class TestReallyLargeTagNumber : pb::IMessage<TestReallyLargeTagNumber>, pb::IBufferMessage {
+  public sealed partial class TestReallyLargeTagNumber : pb::IMessage<TestReallyLargeTagNumber>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestReallyLargeTagNumber> _parser = new pb::MessageParser<TestReallyLargeTagNumber>(() => new TestReallyLargeTagNumber());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2645,9 +3030,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            A = input.ReadInt32();
+            break;
+          }
+          case 2147483640: {
+            Bb = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2667,10 +3072,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestRecursiveMessage : pb::IMessage<TestRecursiveMessage>, pb::IBufferMessage {
+  public sealed partial class TestRecursiveMessage : pb::IMessage<TestRecursiveMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestRecursiveMessage> _parser = new pb::MessageParser<TestRecursiveMessage>(() => new TestRecursiveMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2810,9 +3220,32 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (a_ == null) {
+              A = new global::Google.Protobuf.TestProtos.TestRecursiveMessage();
+            }
+            input.ReadMessage(A);
+            break;
+          }
+          case 16: {
+            I = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2835,13 +3268,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test that mutual recursion works.
   /// </summary>
-  public sealed partial class TestMutualRecursionA : pb::IMessage<TestMutualRecursionA>, pb::IBufferMessage {
+  public sealed partial class TestMutualRecursionA : pb::IMessage<TestMutualRecursionA>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestMutualRecursionA> _parser = new pb::MessageParser<TestMutualRecursionA>(() => new TestMutualRecursionA());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2957,9 +3395,28 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (bb_ == null) {
+              Bb = new global::Google.Protobuf.TestProtos.TestMutualRecursionB();
+            }
+            input.ReadMessage(Bb);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2978,10 +3435,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestMutualRecursionB : pb::IMessage<TestMutualRecursionB>, pb::IBufferMessage {
+  public sealed partial class TestMutualRecursionB : pb::IMessage<TestMutualRecursionB>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestMutualRecursionB> _parser = new pb::MessageParser<TestMutualRecursionB>(() => new TestMutualRecursionB());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3121,9 +3583,32 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (a_ == null) {
+              A = new global::Google.Protobuf.TestProtos.TestMutualRecursionA();
+            }
+            input.ReadMessage(A);
+            break;
+          }
+          case 16: {
+            OptionalInt32 = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -3146,10 +3631,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestEnumAllowAlias : pb::IMessage<TestEnumAllowAlias>, pb::IBufferMessage {
+  public sealed partial class TestEnumAllowAlias : pb::IMessage<TestEnumAllowAlias>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestEnumAllowAlias> _parser = new pb::MessageParser<TestEnumAllowAlias>(() => new TestEnumAllowAlias());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3262,9 +3752,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Value = (global::Google.Protobuf.TestProtos.TestEnumWithDupValue) input.ReadEnum();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -3280,6 +3786,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -3287,7 +3794,11 @@
   /// Test message with CamelCase field names.  This violates Protocol Buffer
   /// standard style.
   /// </summary>
-  public sealed partial class TestCamelCaseFieldNames : pb::IMessage<TestCamelCaseFieldNames>, pb::IBufferMessage {
+  public sealed partial class TestCamelCaseFieldNames : pb::IMessage<TestCamelCaseFieldNames>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestCamelCaseFieldNames> _parser = new pb::MessageParser<TestCamelCaseFieldNames>(() => new TestCamelCaseFieldNames());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3539,9 +4050,58 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            PrimitiveField = input.ReadInt32();
+            break;
+          }
+          case 18: {
+            StringField = input.ReadString();
+            break;
+          }
+          case 24: {
+            EnumField = (global::Google.Protobuf.TestProtos.ForeignEnum) input.ReadEnum();
+            break;
+          }
+          case 34: {
+            if (messageField_ == null) {
+              MessageField = new global::Google.Protobuf.TestProtos.ForeignMessage();
+            }
+            input.ReadMessage(MessageField);
+            break;
+          }
+          case 58:
+          case 56: {
+            repeatedPrimitiveField_.AddEntriesFrom(input, _repeated_repeatedPrimitiveField_codec);
+            break;
+          }
+          case 66: {
+            repeatedStringField_.AddEntriesFrom(input, _repeated_repeatedStringField_codec);
+            break;
+          }
+          case 74:
+          case 72: {
+            repeatedEnumField_.AddEntriesFrom(input, _repeated_repeatedEnumField_codec);
+            break;
+          }
+          case 82: {
+            repeatedMessageField_.AddEntriesFrom(input, _repeated_repeatedMessageField_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -3590,6 +4150,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -3597,7 +4158,11 @@
   /// We list fields out of order, to ensure that we're using field number and not
   /// field index to determine serialization order.
   /// </summary>
-  public sealed partial class TestFieldOrderings : pb::IMessage<TestFieldOrderings>, pb::IBufferMessage {
+  public sealed partial class TestFieldOrderings : pb::IMessage<TestFieldOrderings>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestFieldOrderings> _parser = new pb::MessageParser<TestFieldOrderings>(() => new TestFieldOrderings());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3785,9 +4350,40 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            MyInt = input.ReadInt64();
+            break;
+          }
+          case 90: {
+            MyString = input.ReadString();
+            break;
+          }
+          case 813: {
+            MyFloat = input.ReadFloat();
+            break;
+          }
+          case 1602: {
+            if (singleNestedMessage_ == null) {
+              SingleNestedMessage = new global::Google.Protobuf.TestProtos.TestFieldOrderings.Types.NestedMessage();
+            }
+            input.ReadMessage(SingleNestedMessage);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -3818,12 +4414,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestFieldOrderings message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3965,9 +4566,29 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                Bb = input.ReadInt32();
+                break;
+              }
+              case 16: {
+                Oo = input.ReadInt64();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -3987,6 +4608,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -3995,7 +4617,11 @@
 
   }
 
-  public sealed partial class SparseEnumMessage : pb::IMessage<SparseEnumMessage>, pb::IBufferMessage {
+  public sealed partial class SparseEnumMessage : pb::IMessage<SparseEnumMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<SparseEnumMessage> _parser = new pb::MessageParser<SparseEnumMessage>(() => new SparseEnumMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4108,9 +4734,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            SparseEnum = (global::Google.Protobuf.TestProtos.TestSparseEnum) input.ReadEnum();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4126,13 +4768,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test String and Bytes: string is for valid UTF-8 strings
   /// </summary>
-  public sealed partial class OneString : pb::IMessage<OneString>, pb::IBufferMessage {
+  public sealed partial class OneString : pb::IMessage<OneString>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<OneString> _parser = new pb::MessageParser<OneString>(() => new OneString());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4245,9 +4892,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Data = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4263,10 +4926,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class MoreString : pb::IMessage<MoreString>, pb::IBufferMessage {
+  public sealed partial class MoreString : pb::IMessage<MoreString>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<MoreString> _parser = new pb::MessageParser<MoreString>(() => new MoreString());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4371,9 +5039,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            data_.AddEntriesFrom(input, _repeated_data_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4389,10 +5073,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class OneBytes : pb::IMessage<OneBytes>, pb::IBufferMessage {
+  public sealed partial class OneBytes : pb::IMessage<OneBytes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<OneBytes> _parser = new pb::MessageParser<OneBytes>(() => new OneBytes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4505,9 +5194,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Data = input.ReadBytes();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4523,10 +5228,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class MoreBytes : pb::IMessage<MoreBytes>, pb::IBufferMessage {
+  public sealed partial class MoreBytes : pb::IMessage<MoreBytes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<MoreBytes> _parser = new pb::MessageParser<MoreBytes>(() => new MoreBytes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4639,9 +5349,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Data = input.ReadBytes();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4657,13 +5383,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test int32, uint32, int64, uint64, and bool are all compatible
   /// </summary>
-  public sealed partial class Int32Message : pb::IMessage<Int32Message>, pb::IBufferMessage {
+  public sealed partial class Int32Message : pb::IMessage<Int32Message>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Int32Message> _parser = new pb::MessageParser<Int32Message>(() => new Int32Message());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4776,9 +5507,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Data = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4794,10 +5541,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class Uint32Message : pb::IMessage<Uint32Message>, pb::IBufferMessage {
+  public sealed partial class Uint32Message : pb::IMessage<Uint32Message>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Uint32Message> _parser = new pb::MessageParser<Uint32Message>(() => new Uint32Message());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4910,9 +5662,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Data = input.ReadUInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4928,10 +5696,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class Int64Message : pb::IMessage<Int64Message>, pb::IBufferMessage {
+  public sealed partial class Int64Message : pb::IMessage<Int64Message>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Int64Message> _parser = new pb::MessageParser<Int64Message>(() => new Int64Message());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5044,9 +5817,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Data = input.ReadInt64();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5062,10 +5851,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class Uint64Message : pb::IMessage<Uint64Message>, pb::IBufferMessage {
+  public sealed partial class Uint64Message : pb::IMessage<Uint64Message>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Uint64Message> _parser = new pb::MessageParser<Uint64Message>(() => new Uint64Message());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5178,9 +5972,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Data = input.ReadUInt64();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5196,10 +6006,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class BoolMessage : pb::IMessage<BoolMessage>, pb::IBufferMessage {
+  public sealed partial class BoolMessage : pb::IMessage<BoolMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<BoolMessage> _parser = new pb::MessageParser<BoolMessage>(() => new BoolMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5312,9 +6127,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Data = input.ReadBool();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5330,13 +6161,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test oneofs.
   /// </summary>
-  public sealed partial class TestOneof : pb::IMessage<TestOneof>, pb::IBufferMessage {
+  public sealed partial class TestOneof : pb::IMessage<TestOneof>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestOneof> _parser = new pb::MessageParser<TestOneof>(() => new TestOneof());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5534,9 +6370,38 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            FooInt = input.ReadInt32();
+            break;
+          }
+          case 18: {
+            FooString = input.ReadString();
+            break;
+          }
+          case 26: {
+            global::Google.Protobuf.TestProtos.TestAllTypes subBuilder = new global::Google.Protobuf.TestProtos.TestAllTypes();
+            if (fooCase_ == FooOneofCase.FooMessage) {
+              subBuilder.MergeFrom(FooMessage);
+            }
+            input.ReadMessage(subBuilder);
+            FooMessage = subBuilder;
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5565,10 +6430,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestPackedTypes : pb::IMessage<TestPackedTypes>, pb::IBufferMessage {
+  public sealed partial class TestPackedTypes : pb::IMessage<TestPackedTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestPackedTypes> _parser = new pb::MessageParser<TestPackedTypes>(() => new TestPackedTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5881,9 +6751,91 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 722:
+          case 720: {
+            packedInt32_.AddEntriesFrom(input, _repeated_packedInt32_codec);
+            break;
+          }
+          case 730:
+          case 728: {
+            packedInt64_.AddEntriesFrom(input, _repeated_packedInt64_codec);
+            break;
+          }
+          case 738:
+          case 736: {
+            packedUint32_.AddEntriesFrom(input, _repeated_packedUint32_codec);
+            break;
+          }
+          case 746:
+          case 744: {
+            packedUint64_.AddEntriesFrom(input, _repeated_packedUint64_codec);
+            break;
+          }
+          case 754:
+          case 752: {
+            packedSint32_.AddEntriesFrom(input, _repeated_packedSint32_codec);
+            break;
+          }
+          case 762:
+          case 760: {
+            packedSint64_.AddEntriesFrom(input, _repeated_packedSint64_codec);
+            break;
+          }
+          case 770:
+          case 773: {
+            packedFixed32_.AddEntriesFrom(input, _repeated_packedFixed32_codec);
+            break;
+          }
+          case 778:
+          case 777: {
+            packedFixed64_.AddEntriesFrom(input, _repeated_packedFixed64_codec);
+            break;
+          }
+          case 786:
+          case 789: {
+            packedSfixed32_.AddEntriesFrom(input, _repeated_packedSfixed32_codec);
+            break;
+          }
+          case 794:
+          case 793: {
+            packedSfixed64_.AddEntriesFrom(input, _repeated_packedSfixed64_codec);
+            break;
+          }
+          case 802:
+          case 805: {
+            packedFloat_.AddEntriesFrom(input, _repeated_packedFloat_codec);
+            break;
+          }
+          case 810:
+          case 809: {
+            packedDouble_.AddEntriesFrom(input, _repeated_packedDouble_codec);
+            break;
+          }
+          case 818:
+          case 816: {
+            packedBool_.AddEntriesFrom(input, _repeated_packedBool_codec);
+            break;
+          }
+          case 826:
+          case 824: {
+            packedEnum_.AddEntriesFrom(input, _repeated_packedEnum_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5965,6 +6917,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -5972,7 +6925,11 @@
   /// A message with the same fields as TestPackedTypes, but without packing. Used
   /// to test packed &lt;-> unpacked wire compatibility.
   /// </summary>
-  public sealed partial class TestUnpackedTypes : pb::IMessage<TestUnpackedTypes>, pb::IBufferMessage {
+  public sealed partial class TestUnpackedTypes : pb::IMessage<TestUnpackedTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestUnpackedTypes> _parser = new pb::MessageParser<TestUnpackedTypes>(() => new TestUnpackedTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6285,9 +7242,91 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 722:
+          case 720: {
+            unpackedInt32_.AddEntriesFrom(input, _repeated_unpackedInt32_codec);
+            break;
+          }
+          case 730:
+          case 728: {
+            unpackedInt64_.AddEntriesFrom(input, _repeated_unpackedInt64_codec);
+            break;
+          }
+          case 738:
+          case 736: {
+            unpackedUint32_.AddEntriesFrom(input, _repeated_unpackedUint32_codec);
+            break;
+          }
+          case 746:
+          case 744: {
+            unpackedUint64_.AddEntriesFrom(input, _repeated_unpackedUint64_codec);
+            break;
+          }
+          case 754:
+          case 752: {
+            unpackedSint32_.AddEntriesFrom(input, _repeated_unpackedSint32_codec);
+            break;
+          }
+          case 762:
+          case 760: {
+            unpackedSint64_.AddEntriesFrom(input, _repeated_unpackedSint64_codec);
+            break;
+          }
+          case 770:
+          case 773: {
+            unpackedFixed32_.AddEntriesFrom(input, _repeated_unpackedFixed32_codec);
+            break;
+          }
+          case 778:
+          case 777: {
+            unpackedFixed64_.AddEntriesFrom(input, _repeated_unpackedFixed64_codec);
+            break;
+          }
+          case 786:
+          case 789: {
+            unpackedSfixed32_.AddEntriesFrom(input, _repeated_unpackedSfixed32_codec);
+            break;
+          }
+          case 794:
+          case 793: {
+            unpackedSfixed64_.AddEntriesFrom(input, _repeated_unpackedSfixed64_codec);
+            break;
+          }
+          case 802:
+          case 805: {
+            unpackedFloat_.AddEntriesFrom(input, _repeated_unpackedFloat_codec);
+            break;
+          }
+          case 810:
+          case 809: {
+            unpackedDouble_.AddEntriesFrom(input, _repeated_unpackedDouble_codec);
+            break;
+          }
+          case 818:
+          case 816: {
+            unpackedBool_.AddEntriesFrom(input, _repeated_unpackedBool_codec);
+            break;
+          }
+          case 826:
+          case 824: {
+            unpackedEnum_.AddEntriesFrom(input, _repeated_unpackedEnum_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6369,10 +7408,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestRepeatedScalarDifferentTagSizes : pb::IMessage<TestRepeatedScalarDifferentTagSizes>, pb::IBufferMessage {
+  public sealed partial class TestRepeatedScalarDifferentTagSizes : pb::IMessage<TestRepeatedScalarDifferentTagSizes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestRepeatedScalarDifferentTagSizes> _parser = new pb::MessageParser<TestRepeatedScalarDifferentTagSizes>(() => new TestRepeatedScalarDifferentTagSizes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6571,9 +7615,51 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 98:
+          case 101: {
+            repeatedFixed32_.AddEntriesFrom(input, _repeated_repeatedFixed32_codec);
+            break;
+          }
+          case 106:
+          case 104: {
+            repeatedInt32_.AddEntriesFrom(input, _repeated_repeatedInt32_codec);
+            break;
+          }
+          case 16370:
+          case 16369: {
+            repeatedFixed64_.AddEntriesFrom(input, _repeated_repeatedFixed64_codec);
+            break;
+          }
+          case 16378:
+          case 16376: {
+            repeatedInt64_.AddEntriesFrom(input, _repeated_repeatedInt64_codec);
+            break;
+          }
+          case 2097138:
+          case 2097141: {
+            repeatedFloat_.AddEntriesFrom(input, _repeated_repeatedFloat_codec);
+            break;
+          }
+          case 2097146:
+          case 2097144: {
+            repeatedUint64_.AddEntriesFrom(input, _repeated_repeatedUint64_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6615,10 +7701,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestCommentInjectionMessage : pb::IMessage<TestCommentInjectionMessage>, pb::IBufferMessage {
+  public sealed partial class TestCommentInjectionMessage : pb::IMessage<TestCommentInjectionMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestCommentInjectionMessage> _parser = new pb::MessageParser<TestCommentInjectionMessage>(() => new TestCommentInjectionMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6734,9 +7825,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            A = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6752,13 +7859,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Test that RPC services work.
   /// </summary>
-  public sealed partial class FooRequest : pb::IMessage<FooRequest>, pb::IBufferMessage {
+  public sealed partial class FooRequest : pb::IMessage<FooRequest>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FooRequest> _parser = new pb::MessageParser<FooRequest>(() => new FooRequest());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6847,9 +7959,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6861,10 +7985,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class FooResponse : pb::IMessage<FooResponse>, pb::IBufferMessage {
+  public sealed partial class FooResponse : pb::IMessage<FooResponse>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FooResponse> _parser = new pb::MessageParser<FooResponse>(() => new FooResponse());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6953,9 +8082,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6967,10 +8108,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class FooClientMessage : pb::IMessage<FooClientMessage>, pb::IBufferMessage {
+  public sealed partial class FooClientMessage : pb::IMessage<FooClientMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FooClientMessage> _parser = new pb::MessageParser<FooClientMessage>(() => new FooClientMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7059,9 +8205,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -7073,10 +8231,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class FooServerMessage : pb::IMessage<FooServerMessage>, pb::IBufferMessage {
+  public sealed partial class FooServerMessage : pb::IMessage<FooServerMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FooServerMessage> _parser = new pb::MessageParser<FooServerMessage>(() => new FooServerMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7165,9 +8328,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -7179,10 +8354,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class BarRequest : pb::IMessage<BarRequest>, pb::IBufferMessage {
+  public sealed partial class BarRequest : pb::IMessage<BarRequest>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<BarRequest> _parser = new pb::MessageParser<BarRequest>(() => new BarRequest());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7271,9 +8451,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -7285,10 +8477,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class BarResponse : pb::IMessage<BarResponse>, pb::IBufferMessage {
+  public sealed partial class BarResponse : pb::IMessage<BarResponse>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<BarResponse> _parser = new pb::MessageParser<BarResponse>(() => new BarResponse());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7377,9 +8574,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -7391,10 +8600,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class TestEmptyMessage : pb::IMessage<TestEmptyMessage>, pb::IBufferMessage {
+  public sealed partial class TestEmptyMessage : pb::IMessage<TestEmptyMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestEmptyMessage> _parser = new pb::MessageParser<TestEmptyMessage>(() => new TestEmptyMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7483,9 +8697,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -7497,13 +8723,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// This is a leading comment
   /// </summary>
-  public sealed partial class CommentMessage : pb::IMessage<CommentMessage>, pb::IBufferMessage {
+  public sealed partial class CommentMessage : pb::IMessage<CommentMessage>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<CommentMessage> _parser = new pb::MessageParser<CommentMessage>(() => new CommentMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7619,9 +8850,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Text = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -7637,6 +8884,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the CommentMessage message type.</summary>
@@ -7655,7 +8903,11 @@
       /// <summary>
       /// Leading nested message comment
       /// </summary>
-      public sealed partial class NestedCommentMessage : pb::IMessage<NestedCommentMessage>, pb::IBufferMessage {
+      public sealed partial class NestedCommentMessage : pb::IMessage<NestedCommentMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedCommentMessage> _parser = new pb::MessageParser<NestedCommentMessage>(() => new NestedCommentMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7771,9 +9023,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 10: {
+                NestedText = input.ReadString();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -7789,6 +9057,7 @@
             }
           }
         }
+        #endif
 
       }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestProto3Optional.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestProto3Optional.cs
index 21e55f7..c8cd7f7 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestProto3Optional.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestProto3Optional.cs
@@ -67,7 +67,11 @@
 
   }
   #region Messages
-  public sealed partial class TestProto3Optional : pb::IMessage<TestProto3Optional>, pb::IBufferMessage {
+  public sealed partial class TestProto3Optional : pb::IMessage<TestProto3Optional>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestProto3Optional> _parser = new pb::MessageParser<TestProto3Optional>(() => new TestProto3Optional());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -858,9 +862,111 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            OptionalInt32 = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            OptionalInt64 = input.ReadInt64();
+            break;
+          }
+          case 24: {
+            OptionalUint32 = input.ReadUInt32();
+            break;
+          }
+          case 32: {
+            OptionalUint64 = input.ReadUInt64();
+            break;
+          }
+          case 40: {
+            OptionalSint32 = input.ReadSInt32();
+            break;
+          }
+          case 48: {
+            OptionalSint64 = input.ReadSInt64();
+            break;
+          }
+          case 61: {
+            OptionalFixed32 = input.ReadFixed32();
+            break;
+          }
+          case 65: {
+            OptionalFixed64 = input.ReadFixed64();
+            break;
+          }
+          case 77: {
+            OptionalSfixed32 = input.ReadSFixed32();
+            break;
+          }
+          case 81: {
+            OptionalSfixed64 = input.ReadSFixed64();
+            break;
+          }
+          case 93: {
+            OptionalFloat = input.ReadFloat();
+            break;
+          }
+          case 97: {
+            OptionalDouble = input.ReadDouble();
+            break;
+          }
+          case 104: {
+            OptionalBool = input.ReadBool();
+            break;
+          }
+          case 114: {
+            OptionalString = input.ReadString();
+            break;
+          }
+          case 122: {
+            OptionalBytes = input.ReadBytes();
+            break;
+          }
+          case 130: {
+            OptionalCord = input.ReadString();
+            break;
+          }
+          case 146: {
+            if (optionalNestedMessage_ == null) {
+              OptionalNestedMessage = new global::ProtobufUnittest.TestProto3Optional.Types.NestedMessage();
+            }
+            input.ReadMessage(OptionalNestedMessage);
+            break;
+          }
+          case 154: {
+            if (lazyNestedMessage_ == null) {
+              LazyNestedMessage = new global::ProtobufUnittest.TestProto3Optional.Types.NestedMessage();
+            }
+            input.ReadMessage(LazyNestedMessage);
+            break;
+          }
+          case 168: {
+            OptionalNestedEnum = (global::ProtobufUnittest.TestProto3Optional.Types.NestedEnum) input.ReadEnum();
+            break;
+          }
+          case 176: {
+            SingularInt32 = input.ReadInt32();
+            break;
+          }
+          case 184: {
+            SingularInt64 = input.ReadInt64();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -962,6 +1068,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the TestProto3Optional message type.</summary>
@@ -978,7 +1085,11 @@
         [pbr::OriginalName("NEG")] Neg = -1,
       }
 
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IBufferMessage {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -1109,9 +1220,25 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                Bb = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -1127,6 +1254,7 @@
             }
           }
         }
+        #endif
 
       }
 
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestSelfreferentialOptions.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestSelfreferentialOptions.cs
index e466d54..4365368 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestSelfreferentialOptions.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestSelfreferentialOptions.cs
@@ -63,7 +63,11 @@
   }
 
   #region Messages
-  public sealed partial class FooOptions : pb::IExtendableMessage<FooOptions>, pb::IBufferMessage {
+  public sealed partial class FooOptions : pb::IExtendableMessage<FooOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FooOptions> _parser = new pb::MessageParser<FooOptions>(() => new FooOptions());
     private pb::UnknownFieldSet _unknownFields;
     private pb::ExtensionSet<FooOptions> _extensions;
@@ -250,9 +254,31 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 8: {
+            IntOpt = input.ReadInt32();
+            break;
+          }
+          case 16: {
+            Foo = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -274,6 +300,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<FooOptions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestWellKnownTypes.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestWellKnownTypes.cs
index c67187e..30c906c 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestWellKnownTypes.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestWellKnownTypes.cs
@@ -179,7 +179,11 @@
   /// Each wrapper type is included separately, as languages
   /// map handle different wrappers in different ways.
   /// </summary>
-  public sealed partial class TestWellKnownTypes : pb::IMessage<TestWellKnownTypes>, pb::IBufferMessage {
+  public sealed partial class TestWellKnownTypes : pb::IMessage<TestWellKnownTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<TestWellKnownTypes> _parser = new pb::MessageParser<TestWellKnownTypes>(() => new TestWellKnownTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -784,9 +788,154 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            if (anyField_ == null) {
+              AnyField = new global::Google.Protobuf.WellKnownTypes.Any();
+            }
+            input.ReadMessage(AnyField);
+            break;
+          }
+          case 18: {
+            if (apiField_ == null) {
+              ApiField = new global::Google.Protobuf.WellKnownTypes.Api();
+            }
+            input.ReadMessage(ApiField);
+            break;
+          }
+          case 26: {
+            if (durationField_ == null) {
+              DurationField = new global::Google.Protobuf.WellKnownTypes.Duration();
+            }
+            input.ReadMessage(DurationField);
+            break;
+          }
+          case 34: {
+            if (emptyField_ == null) {
+              EmptyField = new global::Google.Protobuf.WellKnownTypes.Empty();
+            }
+            input.ReadMessage(EmptyField);
+            break;
+          }
+          case 42: {
+            if (fieldMaskField_ == null) {
+              FieldMaskField = new global::Google.Protobuf.WellKnownTypes.FieldMask();
+            }
+            input.ReadMessage(FieldMaskField);
+            break;
+          }
+          case 50: {
+            if (sourceContextField_ == null) {
+              SourceContextField = new global::Google.Protobuf.WellKnownTypes.SourceContext();
+            }
+            input.ReadMessage(SourceContextField);
+            break;
+          }
+          case 58: {
+            if (structField_ == null) {
+              StructField = new global::Google.Protobuf.WellKnownTypes.Struct();
+            }
+            input.ReadMessage(StructField);
+            break;
+          }
+          case 66: {
+            if (timestampField_ == null) {
+              TimestampField = new global::Google.Protobuf.WellKnownTypes.Timestamp();
+            }
+            input.ReadMessage(TimestampField);
+            break;
+          }
+          case 74: {
+            if (typeField_ == null) {
+              TypeField = new global::Google.Protobuf.WellKnownTypes.Type();
+            }
+            input.ReadMessage(TypeField);
+            break;
+          }
+          case 82: {
+            double? value = _single_doubleField_codec.Read(input);
+            if (doubleField_ == null || value != 0D) {
+              DoubleField = value;
+            }
+            break;
+          }
+          case 90: {
+            float? value = _single_floatField_codec.Read(input);
+            if (floatField_ == null || value != 0F) {
+              FloatField = value;
+            }
+            break;
+          }
+          case 98: {
+            long? value = _single_int64Field_codec.Read(input);
+            if (int64Field_ == null || value != 0L) {
+              Int64Field = value;
+            }
+            break;
+          }
+          case 106: {
+            ulong? value = _single_uint64Field_codec.Read(input);
+            if (uint64Field_ == null || value != 0UL) {
+              Uint64Field = value;
+            }
+            break;
+          }
+          case 114: {
+            int? value = _single_int32Field_codec.Read(input);
+            if (int32Field_ == null || value != 0) {
+              Int32Field = value;
+            }
+            break;
+          }
+          case 122: {
+            uint? value = _single_uint32Field_codec.Read(input);
+            if (uint32Field_ == null || value != 0) {
+              Uint32Field = value;
+            }
+            break;
+          }
+          case 130: {
+            bool? value = _single_boolField_codec.Read(input);
+            if (boolField_ == null || value != false) {
+              BoolField = value;
+            }
+            break;
+          }
+          case 138: {
+            string value = _single_stringField_codec.Read(input);
+            if (stringField_ == null || value != "") {
+              StringField = value;
+            }
+            break;
+          }
+          case 146: {
+            pb::ByteString value = _single_bytesField_codec.Read(input);
+            if (bytesField_ == null || value != pb::ByteString.Empty) {
+              BytesField = value;
+            }
+            break;
+          }
+          case 154: {
+            if (valueField_ == null) {
+              ValueField = new global::Google.Protobuf.WellKnownTypes.Value();
+            }
+            input.ReadMessage(ValueField);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -931,13 +1080,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// A repeated field for each well-known type.
   /// </summary>
-  public sealed partial class RepeatedWellKnownTypes : pb::IMessage<RepeatedWellKnownTypes>, pb::IBufferMessage {
+  public sealed partial class RepeatedWellKnownTypes : pb::IMessage<RepeatedWellKnownTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<RepeatedWellKnownTypes> _parser = new pb::MessageParser<RepeatedWellKnownTypes>(() => new RepeatedWellKnownTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1317,9 +1471,93 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            anyField_.AddEntriesFrom(input, _repeated_anyField_codec);
+            break;
+          }
+          case 18: {
+            apiField_.AddEntriesFrom(input, _repeated_apiField_codec);
+            break;
+          }
+          case 26: {
+            durationField_.AddEntriesFrom(input, _repeated_durationField_codec);
+            break;
+          }
+          case 34: {
+            emptyField_.AddEntriesFrom(input, _repeated_emptyField_codec);
+            break;
+          }
+          case 42: {
+            fieldMaskField_.AddEntriesFrom(input, _repeated_fieldMaskField_codec);
+            break;
+          }
+          case 50: {
+            sourceContextField_.AddEntriesFrom(input, _repeated_sourceContextField_codec);
+            break;
+          }
+          case 58: {
+            structField_.AddEntriesFrom(input, _repeated_structField_codec);
+            break;
+          }
+          case 66: {
+            timestampField_.AddEntriesFrom(input, _repeated_timestampField_codec);
+            break;
+          }
+          case 74: {
+            typeField_.AddEntriesFrom(input, _repeated_typeField_codec);
+            break;
+          }
+          case 82: {
+            doubleField_.AddEntriesFrom(input, _repeated_doubleField_codec);
+            break;
+          }
+          case 90: {
+            floatField_.AddEntriesFrom(input, _repeated_floatField_codec);
+            break;
+          }
+          case 98: {
+            int64Field_.AddEntriesFrom(input, _repeated_int64Field_codec);
+            break;
+          }
+          case 106: {
+            uint64Field_.AddEntriesFrom(input, _repeated_uint64Field_codec);
+            break;
+          }
+          case 114: {
+            int32Field_.AddEntriesFrom(input, _repeated_int32Field_codec);
+            break;
+          }
+          case 122: {
+            uint32Field_.AddEntriesFrom(input, _repeated_uint32Field_codec);
+            break;
+          }
+          case 130: {
+            boolField_.AddEntriesFrom(input, _repeated_boolField_codec);
+            break;
+          }
+          case 138: {
+            stringField_.AddEntriesFrom(input, _repeated_stringField_codec);
+            break;
+          }
+          case 146: {
+            bytesField_.AddEntriesFrom(input, _repeated_bytesField_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1403,10 +1641,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class OneofWellKnownTypes : pb::IMessage<OneofWellKnownTypes>, pb::IBufferMessage {
+  public sealed partial class OneofWellKnownTypes : pb::IMessage<OneofWellKnownTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<OneofWellKnownTypes> _parser = new pb::MessageParser<OneofWellKnownTypes>(() => new OneofWellKnownTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2033,9 +2276,138 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            global::Google.Protobuf.WellKnownTypes.Any subBuilder = new global::Google.Protobuf.WellKnownTypes.Any();
+            if (oneofFieldCase_ == OneofFieldOneofCase.AnyField) {
+              subBuilder.MergeFrom(AnyField);
+            }
+            input.ReadMessage(subBuilder);
+            AnyField = subBuilder;
+            break;
+          }
+          case 18: {
+            global::Google.Protobuf.WellKnownTypes.Api subBuilder = new global::Google.Protobuf.WellKnownTypes.Api();
+            if (oneofFieldCase_ == OneofFieldOneofCase.ApiField) {
+              subBuilder.MergeFrom(ApiField);
+            }
+            input.ReadMessage(subBuilder);
+            ApiField = subBuilder;
+            break;
+          }
+          case 26: {
+            global::Google.Protobuf.WellKnownTypes.Duration subBuilder = new global::Google.Protobuf.WellKnownTypes.Duration();
+            if (oneofFieldCase_ == OneofFieldOneofCase.DurationField) {
+              subBuilder.MergeFrom(DurationField);
+            }
+            input.ReadMessage(subBuilder);
+            DurationField = subBuilder;
+            break;
+          }
+          case 34: {
+            global::Google.Protobuf.WellKnownTypes.Empty subBuilder = new global::Google.Protobuf.WellKnownTypes.Empty();
+            if (oneofFieldCase_ == OneofFieldOneofCase.EmptyField) {
+              subBuilder.MergeFrom(EmptyField);
+            }
+            input.ReadMessage(subBuilder);
+            EmptyField = subBuilder;
+            break;
+          }
+          case 42: {
+            global::Google.Protobuf.WellKnownTypes.FieldMask subBuilder = new global::Google.Protobuf.WellKnownTypes.FieldMask();
+            if (oneofFieldCase_ == OneofFieldOneofCase.FieldMaskField) {
+              subBuilder.MergeFrom(FieldMaskField);
+            }
+            input.ReadMessage(subBuilder);
+            FieldMaskField = subBuilder;
+            break;
+          }
+          case 50: {
+            global::Google.Protobuf.WellKnownTypes.SourceContext subBuilder = new global::Google.Protobuf.WellKnownTypes.SourceContext();
+            if (oneofFieldCase_ == OneofFieldOneofCase.SourceContextField) {
+              subBuilder.MergeFrom(SourceContextField);
+            }
+            input.ReadMessage(subBuilder);
+            SourceContextField = subBuilder;
+            break;
+          }
+          case 58: {
+            global::Google.Protobuf.WellKnownTypes.Struct subBuilder = new global::Google.Protobuf.WellKnownTypes.Struct();
+            if (oneofFieldCase_ == OneofFieldOneofCase.StructField) {
+              subBuilder.MergeFrom(StructField);
+            }
+            input.ReadMessage(subBuilder);
+            StructField = subBuilder;
+            break;
+          }
+          case 66: {
+            global::Google.Protobuf.WellKnownTypes.Timestamp subBuilder = new global::Google.Protobuf.WellKnownTypes.Timestamp();
+            if (oneofFieldCase_ == OneofFieldOneofCase.TimestampField) {
+              subBuilder.MergeFrom(TimestampField);
+            }
+            input.ReadMessage(subBuilder);
+            TimestampField = subBuilder;
+            break;
+          }
+          case 74: {
+            global::Google.Protobuf.WellKnownTypes.Type subBuilder = new global::Google.Protobuf.WellKnownTypes.Type();
+            if (oneofFieldCase_ == OneofFieldOneofCase.TypeField) {
+              subBuilder.MergeFrom(TypeField);
+            }
+            input.ReadMessage(subBuilder);
+            TypeField = subBuilder;
+            break;
+          }
+          case 82: {
+            DoubleField = _oneof_doubleField_codec.Read(input);
+            break;
+          }
+          case 90: {
+            FloatField = _oneof_floatField_codec.Read(input);
+            break;
+          }
+          case 98: {
+            Int64Field = _oneof_int64Field_codec.Read(input);
+            break;
+          }
+          case 106: {
+            Uint64Field = _oneof_uint64Field_codec.Read(input);
+            break;
+          }
+          case 114: {
+            Int32Field = _oneof_int32Field_codec.Read(input);
+            break;
+          }
+          case 122: {
+            Uint32Field = _oneof_uint32Field_codec.Read(input);
+            break;
+          }
+          case 130: {
+            BoolField = _oneof_boolField_codec.Read(input);
+            break;
+          }
+          case 138: {
+            StringField = _oneof_stringField_codec.Read(input);
+            break;
+          }
+          case 146: {
+            BytesField = _oneof_bytesField_codec.Read(input);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2164,6 +2536,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -2172,7 +2545,11 @@
   /// need to worry about the value part of the map being the
   /// well-known types, as messages can't be map keys.
   /// </summary>
-  public sealed partial class MapWellKnownTypes : pb::IMessage<MapWellKnownTypes>, pb::IBufferMessage {
+  public sealed partial class MapWellKnownTypes : pb::IMessage<MapWellKnownTypes>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<MapWellKnownTypes> _parser = new pb::MessageParser<MapWellKnownTypes>(() => new MapWellKnownTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2549,9 +2926,93 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            anyField_.AddEntriesFrom(input, _map_anyField_codec);
+            break;
+          }
+          case 18: {
+            apiField_.AddEntriesFrom(input, _map_apiField_codec);
+            break;
+          }
+          case 26: {
+            durationField_.AddEntriesFrom(input, _map_durationField_codec);
+            break;
+          }
+          case 34: {
+            emptyField_.AddEntriesFrom(input, _map_emptyField_codec);
+            break;
+          }
+          case 42: {
+            fieldMaskField_.AddEntriesFrom(input, _map_fieldMaskField_codec);
+            break;
+          }
+          case 50: {
+            sourceContextField_.AddEntriesFrom(input, _map_sourceContextField_codec);
+            break;
+          }
+          case 58: {
+            structField_.AddEntriesFrom(input, _map_structField_codec);
+            break;
+          }
+          case 66: {
+            timestampField_.AddEntriesFrom(input, _map_timestampField_codec);
+            break;
+          }
+          case 74: {
+            typeField_.AddEntriesFrom(input, _map_typeField_codec);
+            break;
+          }
+          case 82: {
+            doubleField_.AddEntriesFrom(input, _map_doubleField_codec);
+            break;
+          }
+          case 90: {
+            floatField_.AddEntriesFrom(input, _map_floatField_codec);
+            break;
+          }
+          case 98: {
+            int64Field_.AddEntriesFrom(input, _map_int64Field_codec);
+            break;
+          }
+          case 106: {
+            uint64Field_.AddEntriesFrom(input, _map_uint64Field_codec);
+            break;
+          }
+          case 114: {
+            int32Field_.AddEntriesFrom(input, _map_int32Field_codec);
+            break;
+          }
+          case 122: {
+            uint32Field_.AddEntriesFrom(input, _map_uint32Field_codec);
+            break;
+          }
+          case 130: {
+            boolField_.AddEntriesFrom(input, _map_boolField_codec);
+            break;
+          }
+          case 138: {
+            stringField_.AddEntriesFrom(input, _map_stringField_codec);
+            break;
+          }
+          case 146: {
+            bytesField_.AddEntriesFrom(input, _map_bytesField_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2635,6 +3096,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf.Test/ByteStringTest.cs b/csharp/src/Google.Protobuf.Test/ByteStringTest.cs
index 84e6341..0ef8d8f 100644
--- a/csharp/src/Google.Protobuf.Test/ByteStringTest.cs
+++ b/csharp/src/Google.Protobuf.Test/ByteStringTest.cs
@@ -233,5 +233,21 @@
             ByteString b2 = ByteString.CopyFrom(200, 1, 2, 3, 4);

             Assert.AreNotEqual(b1.GetHashCode(), b2.GetHashCode());

         }

+

+        [Test]

+        public void GetContentsAsReadOnlySpan()

+        {

+            var byteString = ByteString.CopyFrom(1, 2, 3, 4, 5);

+            var copied = byteString.Span.ToArray();

+            CollectionAssert.AreEqual(byteString, copied);

+        }

+

+        [Test]

+        public void GetContentsAsReadOnlyMemory()

+        {

+            var byteString = ByteString.CopyFrom(1, 2, 3, 4, 5);

+            var copied = byteString.Memory.ToArray();

+            CollectionAssert.AreEqual(byteString, copied);

+        }

     }

 }
\ No newline at end of file
diff --git a/csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs b/csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs
index 527c7d4..61453e5 100644
--- a/csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs
+++ b/csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs
@@ -595,6 +595,95 @@
             Assert.AreEqual(((SampleEnum)(-5)), values[5]);
         }
 
+        [Test]
+        public void TestPackedRepeatedFieldCollectionNonDivisibleLength()
+        {
+            uint tag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var codec = FieldCodec.ForFixed32(tag);
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(tag);
+            output.WriteString("A long string");
+            output.WriteTag(codec.Tag);
+            output.WriteRawVarint32((uint)codec.FixedSize - 1); // Length not divisible by FixedSize
+            output.WriteFixed32(uint.MaxValue);
+            output.Flush();
+            stream.Position = 0;
+
+            var input = new CodedInputStream(stream);
+            input.ReadTag();
+            input.ReadString();
+            input.ReadTag();
+            var field = new RepeatedField<uint>();
+            Assert.Throws<InvalidProtocolBufferException>(() => field.AddEntriesFrom(input, codec));
+
+            // Collection was not pre-initialized
+            Assert.AreEqual(0, field.Count);
+        }
+
+        [Test]
+        public void TestPackedRepeatedFieldCollectionNotAllocatedWhenLengthExceedsBuffer()
+        {
+            uint tag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var codec = FieldCodec.ForFixed32(tag);
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(tag);
+            output.WriteString("A long string");
+            output.WriteTag(codec.Tag);
+            output.WriteRawVarint32((uint)codec.FixedSize);
+            // Note that there is no content for the packed field.
+            // The field length exceeds the remaining length of content.
+            output.Flush();
+            stream.Position = 0;
+
+            var input = new CodedInputStream(stream);
+            input.ReadTag();
+            input.ReadString();
+            input.ReadTag();
+            var field = new RepeatedField<uint>();
+            Assert.Throws<InvalidProtocolBufferException>(() => field.AddEntriesFrom(input, codec));
+
+            // Collection was not pre-initialized
+            Assert.AreEqual(0, field.Count);
+        }
+
+        [Test]
+        public void TestPackedRepeatedFieldCollectionNotAllocatedWhenLengthExceedsRemainingData()
+        {
+            uint tag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var codec = FieldCodec.ForFixed32(tag);
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(tag);
+            output.WriteString("A long string");
+            output.WriteTag(codec.Tag);
+            output.WriteRawVarint32((uint)codec.FixedSize);
+            // Note that there is no content for the packed field.
+            // The field length exceeds the remaining length of the buffer.
+            output.Flush();
+            stream.Position = 0;
+
+            var sequence = ReadOnlySequenceFactory.CreateWithContent(stream.ToArray());
+            ParseContext.Initialize(sequence, out ParseContext ctx);
+
+            ctx.ReadTag();
+            ctx.ReadString();
+            ctx.ReadTag();
+            var field = new RepeatedField<uint>();
+            try
+            {
+                field.AddEntriesFrom(ref ctx, codec);
+                Assert.Fail();
+            }
+            catch (InvalidProtocolBufferException)
+            {
+            }
+
+            // Collection was not pre-initialized
+            Assert.AreEqual(0, field.Count);
+        }
+
         // Fairly perfunctory tests for the non-generic IList implementation
         [Test]
         public void IList_Indexer()
diff --git a/csharp/src/Google.Protobuf.Test/JsonFormatterTest.cs b/csharp/src/Google.Protobuf.Test/JsonFormatterTest.cs
index b07a841..5e9730b 100644
--- a/csharp/src/Google.Protobuf.Test/JsonFormatterTest.cs
+++ b/csharp/src/Google.Protobuf.Test/JsonFormatterTest.cs
@@ -40,6 +40,7 @@
 using static Google.Protobuf.JsonParserTest; // For WrapInQuotes
 using System.IO;
 using Google.Protobuf.Collections;
+using ProtobufUnittest;
 
 namespace Google.Protobuf
 {
@@ -154,6 +155,48 @@
         }
 
         [Test]
+        public void WithFormatDefaultValues_DoesNotAffectMessageFields()
+        {
+            var message = new TestAllTypes();
+            var formatter = new JsonFormatter(JsonFormatter.Settings.Default.WithFormatDefaultValues(true));
+            var json = formatter.Format(message);
+            Assert.IsFalse(json.Contains("\"singleNestedMessage\""));
+            Assert.IsFalse(json.Contains("\"singleForeignMessage\""));
+            Assert.IsFalse(json.Contains("\"singleImportMessage\""));
+        }
+
+        [Test]
+        public void WithFormatDefaultValues_DoesNotAffectProto3OptionalFields()
+        {
+            var message = new TestProto3Optional();
+            message.OptionalInt32 = 0;
+            var formatter = new JsonFormatter(JsonFormatter.Settings.Default.WithFormatDefaultValues(true));
+            var json = formatter.Format(message);
+            // The non-optional proto3 fields are formatted, as is the optional-but-specified field.
+            AssertJson("{ 'optionalInt32': 0, 'singularInt32': 0, 'singularInt64': '0' }", json);
+        }
+
+        [Test]
+        public void WithFormatDefaultValues_DoesNotAffectProto2Fields()
+        {
+            var message = new TestProtos.Proto2.ForeignMessage();
+            message.C = 0;
+            var formatter = new JsonFormatter(JsonFormatter.Settings.Default.WithFormatDefaultValues(true));
+            var json = formatter.Format(message);
+            // The specified field is formatted, but the non-specified field (d) is not.
+            AssertJson("{ 'c': 0 }", json);
+        }
+
+        [Test]
+        public void WithFormatDefaultValues_DoesNotAffectOneofFields()
+        {
+            var message = new TestOneof();
+            var formatter = new JsonFormatter(JsonFormatter.Settings.Default.WithFormatDefaultValues(true));
+            var json = formatter.Format(message);
+            AssertJson("{ }", json);
+        }
+
+        [Test]
         public void RepeatedField()
         {
             AssertJson("{ 'repeatedInt32': [ 1, 2, 3, 4, 5 ] }",
@@ -313,14 +356,16 @@
         }
 
         [Test]
-        public void WrapperFormatting_IncludeNull()
+        public void WrapperFormatting_FormatDefaultValuesDoesNotFormatNull()
         {
             // The actual JSON here is very large because there are lots of fields. Just test a couple of them.
             var message = new TestWellKnownTypes { Int32Field = 10 };
             var formatter = new JsonFormatter(JsonFormatter.Settings.Default.WithFormatDefaultValues(true));
             var actualJson = formatter.Format(message);
-            Assert.IsTrue(actualJson.Contains("\"int64Field\": null"));
-            Assert.IsFalse(actualJson.Contains("\"int32Field\": null"));
+            // This *used* to include "int64Field": null, but that was a bug.
+            // WithDefaultValues should not affect message fields, including wrapper types.
+            Assert.IsFalse(actualJson.Contains("\"int64Field\": null"));
+            Assert.IsTrue(actualJson.Contains("\"int32Field\": 10"));
         }
 
         [Test]
@@ -602,6 +647,13 @@
             AssertWriteValue(value, "[ 1, 2, 3 ]");
         }
 
+        [Test]
+        public void Proto2_DefaultValuesWritten()
+        {
+            var value = new ProtobufTestMessages.Proto2.TestAllTypesProto2() { FieldName13 = 0 };
+            AssertWriteValue(value, "{ 'FieldName13': 0 }");
+        }
+
         private static void AssertWriteValue(object value, string expectedJson)
         {
             var writer = new StringWriter();
diff --git a/csharp/src/Google.Protobuf.Test/JsonParserTest.cs b/csharp/src/Google.Protobuf.Test/JsonParserTest.cs
index a6cf04a..f9f8cde 100644
--- a/csharp/src/Google.Protobuf.Test/JsonParserTest.cs
+++ b/csharp/src/Google.Protobuf.Test/JsonParserTest.cs
@@ -34,6 +34,7 @@
 using Google.Protobuf.TestProtos;
 using Google.Protobuf.WellKnownTypes;
 using NUnit.Framework;
+using ProtobufTestMessages.Proto2;
 using System;
 
 namespace Google.Protobuf
@@ -950,6 +951,16 @@
         }
 
         [Test]
+        public void Proto2_DefaultValuesPreserved()
+        {
+            string json = "{ \"FieldName13\": 0 }";
+            var parsed = TestAllTypesProto2.Parser.ParseJson(json);
+            Assert.False(parsed.HasFieldName10);
+            Assert.True(parsed.HasFieldName13);
+            Assert.AreEqual(0, parsed.FieldName13);
+        }
+
+        [Test]
         [TestCase("5")]
         [TestCase("\"text\"")]
         [TestCase("[0, 1, 2]")]
diff --git a/csharp/src/Google.Protobuf.Test/ReadOnlySequenceFactory.cs b/csharp/src/Google.Protobuf.Test/ReadOnlySequenceFactory.cs
index d2050d3..588b559 100644
--- a/csharp/src/Google.Protobuf.Test/ReadOnlySequenceFactory.cs
+++ b/csharp/src/Google.Protobuf.Test/ReadOnlySequenceFactory.cs
@@ -50,9 +50,9 @@
             while (currentIndex < data.Length)
             {
                 var segment = new List<byte>();
-                for (; currentIndex < Math.Min(currentIndex + segmentSize, data.Length); currentIndex++)
+                while (segment.Count < segmentSize && currentIndex < data.Length)
                 {
-                    segment.Add(data[currentIndex]);
+                    segment.Add(data[currentIndex++]);
                 }
                 segments.Add(segment.ToArray());
                 segments.Add(new byte[0]);
diff --git a/csharp/src/Google.Protobuf.Test/RefStructCompatibilityTest.cs b/csharp/src/Google.Protobuf.Test/RefStructCompatibilityTest.cs
new file mode 100644
index 0000000..f2d9a2d
--- /dev/null
+++ b/csharp/src/Google.Protobuf.Test/RefStructCompatibilityTest.cs
@@ -0,0 +1,119 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using NUnit.Framework;
+using System.Diagnostics;
+using System;
+using System.Reflection;
+using System.IO;
+
+namespace Google.Protobuf
+{
+    public class RefStructCompatibilityTest
+    {
+        /// <summary>
+        /// Checks that the generated code can be compiler with an old C# compiler.
+        /// The reason why this test is needed is that even though dotnet SDK projects allow to set LangVersion,
+        /// this setting doesn't accurately simulate compilation with an actual old pre-roslyn C# compiler.
+        /// For instance, the "ref struct" types are only supported by C# 7.2 and higher, but even if
+        /// LangVersion is set low, the roslyn compiler still understands the concept of ref struct
+        /// and silently accepts them. Therefore we try to build the generated code with an actual old C# compiler
+        /// to be able to catch these sort of compatibility problems.
+        /// </summary>
+        [Test]
+        public void GeneratedCodeCompilesWithOldCsharpCompiler()
+        {
+            if (Environment.OSVersion.Platform != PlatformID.Win32NT)
+            {
+                // This tests needs old C# compiler which is only available on Windows. Skipping it on all other platforms.
+                return;
+            }
+
+            var currentAssemblyDir = Path.GetDirectoryName(typeof(RefStructCompatibilityTest).GetTypeInfo().Assembly.Location);
+            var testProtosProjectDir = Path.GetFullPath(Path.Combine(currentAssemblyDir, "..", "..", "..", "..", "Google.Protobuf.Test.TestProtos"));
+            var testProtosOutputDir = (currentAssemblyDir.Contains("bin/Debug/") || currentAssemblyDir.Contains("bin\\Debug\\")) ? "bin\\Debug\\net45" : "bin\\Release\\net45";
+
+            // If "ref struct" types are used in the generated code, compilation with an old compiler will fail with the following error:
+            // "XYZ is obsolete: 'Types with embedded references are not supported in this version of your compiler.'"
+            // We build the code with GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE to avoid the use of ref struct in the generated code.
+            var compatibilityFlag = "-define:GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE";
+            var sources = "*.cs";  // the generated sources from the TestProtos project
+            var args = $"-langversion:3 -target:library {compatibilityFlag} -reference:{testProtosOutputDir}\\Google.Protobuf.dll -out:{testProtosOutputDir}\\TestProtos.RefStructCompatibilityTest.OldCompiler.dll {sources}";
+            RunOldCsharpCompilerAndCheckSuccess(args, testProtosProjectDir);
+        }
+
+        /// <summary>
+        /// Invoke an old C# compiler in a subprocess and check it finished successful.
+        /// </summary>
+        /// <param name="args"></param>
+        /// <param name="workingDirectory"></param>
+        private void RunOldCsharpCompilerAndCheckSuccess(string args, string workingDirectory)
+        {  
+            using (var process = new Process())
+            {
+                // Get the path to the old C# 5 compiler from .NET framework. This approach is not 100% reliable, but works on most machines.
+                // Alternative way of getting the framework path is System.Runtime.InteropServices.RuntimeEnvironment.GetRuntimeDirectory()
+                // but it only works with the net45 target.
+                var oldCsharpCompilerPath = Path.Combine(Environment.GetEnvironmentVariable("WINDIR"), "Microsoft.NET", "Framework", "v4.0.30319", "csc.exe");
+                process.StartInfo.FileName = oldCsharpCompilerPath;
+                process.StartInfo.RedirectStandardOutput = true;
+                process.StartInfo.RedirectStandardError = true;
+                process.StartInfo.UseShellExecute = false;
+                process.StartInfo.Arguments = args;
+                process.StartInfo.WorkingDirectory = workingDirectory;
+
+                process.OutputDataReceived += (sender, e) =>
+                {
+                    if (e.Data != null)
+                    {
+                        Console.WriteLine(e.Data);
+                    }
+                };
+                process.ErrorDataReceived += (sender, e) =>
+                {
+                    if (e.Data != null)
+                    {
+                        Console.WriteLine(e.Data);
+                    }
+                };
+
+                process.Start();
+
+                process.BeginErrorReadLine();
+                process.BeginOutputReadLine();
+
+                process.WaitForExit();
+                Assert.AreEqual(0, process.ExitCode);
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/csharp/src/Google.Protobuf/ByteString.cs b/csharp/src/Google.Protobuf/ByteString.cs
index 027c8d8..74dc865 100644
--- a/csharp/src/Google.Protobuf/ByteString.cs
+++ b/csharp/src/Google.Protobuf/ByteString.cs
@@ -34,6 +34,7 @@
 using System.Collections;

 using System.Collections.Generic;

 using System.IO;

+using System.Security;

 using System.Text;

 #if !NET35

 using System.Threading;

@@ -115,13 +116,27 @@
         /// Provides read-only access to the data of this <see cref="ByteString"/>.

         /// No data is copied so this is the most efficient way of accessing.

         /// </summary>

-        public ReadOnlySpan<byte> Span => new ReadOnlySpan<byte>(bytes);

+        public ReadOnlySpan<byte> Span

+        {

+            [SecuritySafeCritical]

+            get

+            {

+                return new ReadOnlySpan<byte>(bytes);

+            }

+        }

 

         /// <summary>

         /// Provides read-only access to the data of this <see cref="ByteString"/>.

         /// No data is copied so this is the most efficient way of accessing.

         /// </summary>

-        public ReadOnlyMemory<byte> Memory => new ReadOnlyMemory<byte>(bytes);

+        public ReadOnlyMemory<byte> Memory

+        {

+            [SecuritySafeCritical]

+            get

+            {

+                return new ReadOnlyMemory<byte>(bytes);

+            }

+        }

 #endif

 

         /// <summary>

diff --git a/csharp/src/Google.Protobuf/Collections/RepeatedField.cs b/csharp/src/Google.Protobuf/Collections/RepeatedField.cs
index 5c39aab..b1bd9b1 100644
--- a/csharp/src/Google.Protobuf/Collections/RepeatedField.cs
+++ b/csharp/src/Google.Protobuf/Collections/RepeatedField.cs
@@ -35,6 +35,7 @@
 using System.Collections.Generic;

 using System.IO;

 using System.Security;

+using System.Threading;

 

 namespace Google.Protobuf.Collections

 {

@@ -126,9 +127,31 @@
                 if (length > 0)

                 {

                     int oldLimit = SegmentedBufferHelper.PushLimit(ref ctx.state, length);

-                    while (!SegmentedBufferHelper.IsReachedLimit(ref ctx.state))

+

+                    // If the content is fixed size then we can calculate the length

+                    // of the repeated field and pre-initialize the underlying collection.

+                    //

+                    // Check that the supplied length doesn't exceed the underlying buffer.

+                    // That prevents a malicious length from initializing a very large collection.

+                    if (codec.FixedSize > 0 && length % codec.FixedSize == 0 && IsDataAvailable(ref ctx, length))

                     {

-                        Add(reader(ref ctx));

+                        EnsureSize(count + (length / codec.FixedSize));

+

+                        while (!SegmentedBufferHelper.IsReachedLimit(ref ctx.state))

+                        {

+                            // Only FieldCodecs with a fixed size can reach here, and they are all known

+                            // types that don't allow the user to specify a custom reader action.

+                            // reader action will never return null.

+                            array[count++] = reader(ref ctx);

+                        }

+                    }

+                    else

+                    {

+                        // Content is variable size so add until we reach the limit.

+                        while (!SegmentedBufferHelper.IsReachedLimit(ref ctx.state))

+                        {

+                            Add(reader(ref ctx));

+                        }

                     }

                     SegmentedBufferHelper.PopLimit(ref ctx.state, oldLimit);

                 }

@@ -144,6 +167,24 @@
             }

         }

 

+        private bool IsDataAvailable(ref ParseContext ctx, int size)

+        {

+            // Data fits in remaining buffer

+            if (size <= ctx.state.bufferSize - ctx.state.bufferPos)

+            {

+                return true;

+            }

+

+            // Data fits in remaining source data.

+            // Note that this will never be true when reading from a stream as the total length is unknown.

+            if (size < ctx.state.segmentedBufferHelper.TotalLength - ctx.state.totalBytesRetired - ctx.state.bufferPos)

+            {

+                return true;

+            }

+

+            return false;

+        }

+

         /// <summary>

         /// Calculates the size of this collection based on the given codec.

         /// </summary>

diff --git a/csharp/src/Google.Protobuf/Google.Protobuf.csproj b/csharp/src/Google.Protobuf/Google.Protobuf.csproj
index 11615c8..db86da5 100644
--- a/csharp/src/Google.Protobuf/Google.Protobuf.csproj
+++ b/csharp/src/Google.Protobuf/Google.Protobuf.csproj
@@ -5,6 +5,7 @@
     <Copyright>Copyright 2015, Google Inc.</Copyright>
     <AssemblyTitle>Google Protocol Buffers</AssemblyTitle>
     <VersionPrefix>3.12.2</VersionPrefix>
+    <VersionPrefix>3.12.3</VersionPrefix>
     <!-- C# 7.2 is required for Span/BufferWriter/ReadOnlySequence -->
     <LangVersion>7.2</LangVersion>
     <Authors>Google Inc.</Authors>
diff --git a/csharp/src/Google.Protobuf/JsonFormatter.cs b/csharp/src/Google.Protobuf/JsonFormatter.cs
index 5aaefe7..699a81d 100644
--- a/csharp/src/Google.Protobuf/JsonFormatter.cs
+++ b/csharp/src/Google.Protobuf/JsonFormatter.cs
@@ -221,19 +221,12 @@
             foreach (var field in fields.InFieldNumberOrder())
             {
                 var accessor = field.Accessor;
-                if (field.ContainingOneof != null && field.ContainingOneof.Accessor.GetCaseFieldDescriptor(message) != field)
-                {
-                    continue;
-                }
-                // Omit default values unless we're asked to format them, or they're oneofs (where the default
-                // value is still formatted regardless, because that's how we preserve the oneof case).
-                object value = accessor.GetValue(message);
-                if (field.ContainingOneof == null && !settings.FormatDefaultValues && IsDefaultValue(accessor, value))
+                var value = accessor.GetValue(message);
+                if (!ShouldFormatFieldValue(message, field, value))
                 {
                     continue;
                 }
 
-                // Okay, all tests complete: let's write the field value...
                 if (!first)
                 {
                     writer.Write(PropertySeparator);
@@ -248,6 +241,18 @@
             return !first;
         }
 
+        /// <summary>
+        /// Determines whether or not a field value should be serialized according to the field,
+        /// its value in the message, and the settings of this formatter.
+        /// </summary>
+        private bool ShouldFormatFieldValue(IMessage message, FieldDescriptor field, object value) =>
+            field.HasPresence
+            // Fields that support presence *just* use that
+            ? field.Accessor.HasValue(message)
+            // Otherwise, format if either we've been asked to format default values, or if it's
+            // not a default value anyway.
+            : settings.FormatDefaultValues || !IsDefaultValue(field, value);
+
         // Converted from java/core/src/main/java/com/google/protobuf/Descriptors.java
         internal static string ToJsonName(string name)
         {
@@ -295,19 +300,19 @@
             writer.Write("null");
         }
 
-        private static bool IsDefaultValue(IFieldAccessor accessor, object value)
+        private static bool IsDefaultValue(FieldDescriptor descriptor, object value)
         {
-            if (accessor.Descriptor.IsMap)
+            if (descriptor.IsMap)
             {
                 IDictionary dictionary = (IDictionary) value;
                 return dictionary.Count == 0;
             }
-            if (accessor.Descriptor.IsRepeated)
+            if (descriptor.IsRepeated)
             {
                 IList list = (IList) value;
                 return list.Count == 0;
             }
-            switch (accessor.Descriptor.FieldType)
+            switch (descriptor.FieldType)
             {
                 case FieldType.Bool:
                     return (bool) value == false;
@@ -793,8 +798,10 @@
             }
 
             /// <summary>
-            /// Whether fields whose values are the default for the field type (e.g. 0 for integers)
-            /// should be formatted (true) or omitted (false).
+            /// Whether fields which would otherwise not be included in the formatted data
+            /// should be formatted even when the value is not present, or has the default value.
+            /// This option only affects fields which don't support "presence" (e.g.
+            /// singular non-optional proto3 primitive fields).
             /// </summary>
             public bool FormatDefaultValues { get; }
 
diff --git a/csharp/src/Google.Protobuf/Reflection/Descriptor.cs b/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
index 3c6e82b..fda5676 100644
--- a/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
+++ b/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
@@ -194,7 +194,11 @@
   /// The protocol compiler can output a FileDescriptorSet containing the .proto
   /// files it parses.
   /// </summary>
-  public sealed partial class FileDescriptorSet : pb::IMessage<FileDescriptorSet>, pb::IBufferMessage {
+  public sealed partial class FileDescriptorSet : pb::IMessage<FileDescriptorSet>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FileDescriptorSet> _parser = new pb::MessageParser<FileDescriptorSet>(() => new FileDescriptorSet());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -299,9 +303,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            file_.AddEntriesFrom(input, _repeated_file_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -317,13 +337,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Describes a complete .proto file.
   /// </summary>
-  public sealed partial class FileDescriptorProto : pb::IMessage<FileDescriptorProto>, pb::IBufferMessage {
+  public sealed partial class FileDescriptorProto : pb::IMessage<FileDescriptorProto>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FileDescriptorProto> _parser = new pb::MessageParser<FileDescriptorProto>(() => new FileDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -715,9 +740,77 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            Package = input.ReadString();
+            break;
+          }
+          case 26: {
+            dependency_.AddEntriesFrom(input, _repeated_dependency_codec);
+            break;
+          }
+          case 34: {
+            messageType_.AddEntriesFrom(input, _repeated_messageType_codec);
+            break;
+          }
+          case 42: {
+            enumType_.AddEntriesFrom(input, _repeated_enumType_codec);
+            break;
+          }
+          case 50: {
+            service_.AddEntriesFrom(input, _repeated_service_codec);
+            break;
+          }
+          case 58: {
+            extension_.AddEntriesFrom(input, _repeated_extension_codec);
+            break;
+          }
+          case 66: {
+            if (options_ == null) {
+              Options = new global::Google.Protobuf.Reflection.FileOptions();
+            }
+            input.ReadMessage(Options);
+            break;
+          }
+          case 74: {
+            if (sourceCodeInfo_ == null) {
+              SourceCodeInfo = new global::Google.Protobuf.Reflection.SourceCodeInfo();
+            }
+            input.ReadMessage(SourceCodeInfo);
+            break;
+          }
+          case 82:
+          case 80: {
+            publicDependency_.AddEntriesFrom(input, _repeated_publicDependency_codec);
+            break;
+          }
+          case 90:
+          case 88: {
+            weakDependency_.AddEntriesFrom(input, _repeated_weakDependency_codec);
+            break;
+          }
+          case 98: {
+            Syntax = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -785,13 +878,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Describes a message type.
   /// </summary>
-  public sealed partial class DescriptorProto : pb::IMessage<DescriptorProto>, pb::IBufferMessage {
+  public sealed partial class DescriptorProto : pb::IMessage<DescriptorProto>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<DescriptorProto> _parser = new pb::MessageParser<DescriptorProto>(() => new DescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1075,9 +1173,64 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            field_.AddEntriesFrom(input, _repeated_field_codec);
+            break;
+          }
+          case 26: {
+            nestedType_.AddEntriesFrom(input, _repeated_nestedType_codec);
+            break;
+          }
+          case 34: {
+            enumType_.AddEntriesFrom(input, _repeated_enumType_codec);
+            break;
+          }
+          case 42: {
+            extensionRange_.AddEntriesFrom(input, _repeated_extensionRange_codec);
+            break;
+          }
+          case 50: {
+            extension_.AddEntriesFrom(input, _repeated_extension_codec);
+            break;
+          }
+          case 58: {
+            if (options_ == null) {
+              Options = new global::Google.Protobuf.Reflection.MessageOptions();
+            }
+            input.ReadMessage(Options);
+            break;
+          }
+          case 66: {
+            oneofDecl_.AddEntriesFrom(input, _repeated_oneofDecl_codec);
+            break;
+          }
+          case 74: {
+            reservedRange_.AddEntriesFrom(input, _repeated_reservedRange_codec);
+            break;
+          }
+          case 82: {
+            reservedName_.AddEntriesFrom(input, _repeated_reservedName_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1132,12 +1285,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the DescriptorProto message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class ExtensionRange : pb::IMessage<ExtensionRange>, pb::IBufferMessage {
+      public sealed partial class ExtensionRange : pb::IMessage<ExtensionRange>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<ExtensionRange> _parser = new pb::MessageParser<ExtensionRange>(() => new ExtensionRange());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -1335,9 +1493,36 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                Start = input.ReadInt32();
+                break;
+              }
+              case 16: {
+                End = input.ReadInt32();
+                break;
+              }
+              case 26: {
+                if (options_ == null) {
+                  Options = new global::Google.Protobuf.Reflection.ExtensionRangeOptions();
+                }
+                input.ReadMessage(Options);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -1364,6 +1549,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -1372,7 +1558,11 @@
       /// fields or extension ranges in the same message. Reserved ranges may
       /// not overlap.
       /// </summary>
-      public sealed partial class ReservedRange : pb::IMessage<ReservedRange>, pb::IBufferMessage {
+      public sealed partial class ReservedRange : pb::IMessage<ReservedRange>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<ReservedRange> _parser = new pb::MessageParser<ReservedRange>(() => new ReservedRange());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -1543,9 +1733,29 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                Start = input.ReadInt32();
+                break;
+              }
+              case 16: {
+                End = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -1565,6 +1775,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -1573,7 +1784,11 @@
 
   }
 
-  public sealed partial class ExtensionRangeOptions : pb::IExtendableMessage<ExtensionRangeOptions>, pb::IBufferMessage {
+  public sealed partial class ExtensionRangeOptions : pb::IExtendableMessage<ExtensionRangeOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ExtensionRangeOptions> _parser = new pb::MessageParser<ExtensionRangeOptions>(() => new ExtensionRangeOptions());
     private pb::UnknownFieldSet _unknownFields;
     internal pb::ExtensionSet<ExtensionRangeOptions> _extensions;
@@ -1697,9 +1912,27 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 7994: {
+            uninterpretedOption_.AddEntriesFrom(input, _repeated_uninterpretedOption_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1717,6 +1950,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<ExtensionRangeOptions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -1745,7 +1979,11 @@
   /// <summary>
   /// Describes a field within a message.
   /// </summary>
-  public sealed partial class FieldDescriptorProto : pb::IMessage<FieldDescriptorProto>, pb::IBufferMessage {
+  public sealed partial class FieldDescriptorProto : pb::IMessage<FieldDescriptorProto>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FieldDescriptorProto> _parser = new pb::MessageParser<FieldDescriptorProto>(() => new FieldDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -2283,9 +2521,68 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            Extendee = input.ReadString();
+            break;
+          }
+          case 24: {
+            Number = input.ReadInt32();
+            break;
+          }
+          case 32: {
+            Label = (global::Google.Protobuf.Reflection.FieldDescriptorProto.Types.Label) input.ReadEnum();
+            break;
+          }
+          case 40: {
+            Type = (global::Google.Protobuf.Reflection.FieldDescriptorProto.Types.Type) input.ReadEnum();
+            break;
+          }
+          case 50: {
+            TypeName = input.ReadString();
+            break;
+          }
+          case 58: {
+            DefaultValue = input.ReadString();
+            break;
+          }
+          case 66: {
+            if (options_ == null) {
+              Options = new global::Google.Protobuf.Reflection.FieldOptions();
+            }
+            input.ReadMessage(Options);
+            break;
+          }
+          case 72: {
+            OneofIndex = input.ReadInt32();
+            break;
+          }
+          case 82: {
+            JsonName = input.ReadString();
+            break;
+          }
+          case 136: {
+            Proto3Optional = input.ReadBool();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2344,6 +2641,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the FieldDescriptorProto message type.</summary>
@@ -2417,7 +2715,11 @@
   /// <summary>
   /// Describes a oneof.
   /// </summary>
-  public sealed partial class OneofDescriptorProto : pb::IMessage<OneofDescriptorProto>, pb::IBufferMessage {
+  public sealed partial class OneofDescriptorProto : pb::IMessage<OneofDescriptorProto>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<OneofDescriptorProto> _parser = new pb::MessageParser<OneofDescriptorProto>(() => new OneofDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2569,9 +2871,32 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            if (options_ == null) {
+              Options = new global::Google.Protobuf.Reflection.OneofOptions();
+            }
+            input.ReadMessage(Options);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2594,13 +2919,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Describes an enum type.
   /// </summary>
-  public sealed partial class EnumDescriptorProto : pb::IMessage<EnumDescriptorProto>, pb::IBufferMessage {
+  public sealed partial class EnumDescriptorProto : pb::IMessage<EnumDescriptorProto>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<EnumDescriptorProto> _parser = new pb::MessageParser<EnumDescriptorProto>(() => new EnumDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2809,9 +3139,44 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            value_.AddEntriesFrom(input, _repeated_value_codec);
+            break;
+          }
+          case 26: {
+            if (options_ == null) {
+              Options = new global::Google.Protobuf.Reflection.EnumOptions();
+            }
+            input.ReadMessage(Options);
+            break;
+          }
+          case 34: {
+            reservedRange_.AddEntriesFrom(input, _repeated_reservedRange_codec);
+            break;
+          }
+          case 42: {
+            reservedName_.AddEntriesFrom(input, _repeated_reservedName_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -2846,6 +3211,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the EnumDescriptorProto message type.</summary>
@@ -2859,7 +3225,11 @@
       /// is inclusive such that it can appropriately represent the entire int32
       /// domain.
       /// </summary>
-      public sealed partial class EnumReservedRange : pb::IMessage<EnumReservedRange>, pb::IBufferMessage {
+      public sealed partial class EnumReservedRange : pb::IMessage<EnumReservedRange>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<EnumReservedRange> _parser = new pb::MessageParser<EnumReservedRange>(() => new EnumReservedRange());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -3030,9 +3400,29 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 8: {
+                Start = input.ReadInt32();
+                break;
+              }
+              case 16: {
+                End = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -3052,6 +3442,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -3063,7 +3454,11 @@
   /// <summary>
   /// Describes a value within an enum.
   /// </summary>
-  public sealed partial class EnumValueDescriptorProto : pb::IMessage<EnumValueDescriptorProto>, pb::IBufferMessage {
+  public sealed partial class EnumValueDescriptorProto : pb::IMessage<EnumValueDescriptorProto>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<EnumValueDescriptorProto> _parser = new pb::MessageParser<EnumValueDescriptorProto>(() => new EnumValueDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -3254,9 +3649,36 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 16: {
+            Number = input.ReadInt32();
+            break;
+          }
+          case 26: {
+            if (options_ == null) {
+              Options = new global::Google.Protobuf.Reflection.EnumValueOptions();
+            }
+            input.ReadMessage(Options);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -3283,13 +3705,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Describes a service.
   /// </summary>
-  public sealed partial class ServiceDescriptorProto : pb::IMessage<ServiceDescriptorProto>, pb::IBufferMessage {
+  public sealed partial class ServiceDescriptorProto : pb::IMessage<ServiceDescriptorProto>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ServiceDescriptorProto> _parser = new pb::MessageParser<ServiceDescriptorProto>(() => new ServiceDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3457,9 +3884,36 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            method_.AddEntriesFrom(input, _repeated_method_codec);
+            break;
+          }
+          case 26: {
+            if (options_ == null) {
+              Options = new global::Google.Protobuf.Reflection.ServiceOptions();
+            }
+            input.ReadMessage(Options);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -3486,13 +3940,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Describes a method of a service.
   /// </summary>
-  public sealed partial class MethodDescriptorProto : pb::IMessage<MethodDescriptorProto>, pb::IBufferMessage {
+  public sealed partial class MethodDescriptorProto : pb::IMessage<MethodDescriptorProto>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<MethodDescriptorProto> _parser = new pb::MessageParser<MethodDescriptorProto>(() => new MethodDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -3802,9 +4261,48 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            InputType = input.ReadString();
+            break;
+          }
+          case 26: {
+            OutputType = input.ReadString();
+            break;
+          }
+          case 34: {
+            if (options_ == null) {
+              Options = new global::Google.Protobuf.Reflection.MethodOptions();
+            }
+            input.ReadMessage(Options);
+            break;
+          }
+          case 40: {
+            ClientStreaming = input.ReadBool();
+            break;
+          }
+          case 48: {
+            ServerStreaming = input.ReadBool();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -3843,10 +4341,15 @@
         }
       }
     }
+    #endif
 
   }
 
-  public sealed partial class FileOptions : pb::IExtendableMessage<FileOptions>, pb::IBufferMessage {
+  public sealed partial class FileOptions : pb::IExtendableMessage<FileOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FileOptions> _parser = new pb::MessageParser<FileOptions>(() => new FileOptions());
     private pb::UnknownFieldSet _unknownFields;
     internal pb::ExtensionSet<FileOptions> _extensions;
@@ -4799,9 +5302,107 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 10: {
+            JavaPackage = input.ReadString();
+            break;
+          }
+          case 66: {
+            JavaOuterClassname = input.ReadString();
+            break;
+          }
+          case 72: {
+            OptimizeFor = (global::Google.Protobuf.Reflection.FileOptions.Types.OptimizeMode) input.ReadEnum();
+            break;
+          }
+          case 80: {
+            JavaMultipleFiles = input.ReadBool();
+            break;
+          }
+          case 90: {
+            GoPackage = input.ReadString();
+            break;
+          }
+          case 128: {
+            CcGenericServices = input.ReadBool();
+            break;
+          }
+          case 136: {
+            JavaGenericServices = input.ReadBool();
+            break;
+          }
+          case 144: {
+            PyGenericServices = input.ReadBool();
+            break;
+          }
+          case 160: {
+            JavaGenerateEqualsAndHash = input.ReadBool();
+            break;
+          }
+          case 184: {
+            Deprecated = input.ReadBool();
+            break;
+          }
+          case 216: {
+            JavaStringCheckUtf8 = input.ReadBool();
+            break;
+          }
+          case 248: {
+            CcEnableArenas = input.ReadBool();
+            break;
+          }
+          case 290: {
+            ObjcClassPrefix = input.ReadString();
+            break;
+          }
+          case 298: {
+            CsharpNamespace = input.ReadString();
+            break;
+          }
+          case 314: {
+            SwiftPrefix = input.ReadString();
+            break;
+          }
+          case 322: {
+            PhpClassPrefix = input.ReadString();
+            break;
+          }
+          case 330: {
+            PhpNamespace = input.ReadString();
+            break;
+          }
+          case 336: {
+            PhpGenericServices = input.ReadBool();
+            break;
+          }
+          case 354: {
+            PhpMetadataNamespace = input.ReadString();
+            break;
+          }
+          case 362: {
+            RubyPackage = input.ReadString();
+            break;
+          }
+          case 7994: {
+            uninterpretedOption_.AddEntriesFrom(input, _repeated_uninterpretedOption_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -4899,6 +5500,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<FileOptions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -4949,7 +5551,11 @@
 
   }
 
-  public sealed partial class MessageOptions : pb::IExtendableMessage<MessageOptions>, pb::IBufferMessage {
+  public sealed partial class MessageOptions : pb::IExtendableMessage<MessageOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<MessageOptions> _parser = new pb::MessageParser<MessageOptions>(() => new MessageOptions());
     private pb::UnknownFieldSet _unknownFields;
     internal pb::ExtensionSet<MessageOptions> _extensions;
@@ -5277,9 +5883,43 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 8: {
+            MessageSetWireFormat = input.ReadBool();
+            break;
+          }
+          case 16: {
+            NoStandardDescriptorAccessor = input.ReadBool();
+            break;
+          }
+          case 24: {
+            Deprecated = input.ReadBool();
+            break;
+          }
+          case 56: {
+            MapEntry = input.ReadBool();
+            break;
+          }
+          case 7994: {
+            uninterpretedOption_.AddEntriesFrom(input, _repeated_uninterpretedOption_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5313,6 +5953,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<MessageOptions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -5338,7 +5979,11 @@
 
   }
 
-  public sealed partial class FieldOptions : pb::IExtendableMessage<FieldOptions>, pb::IBufferMessage {
+  public sealed partial class FieldOptions : pb::IExtendableMessage<FieldOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FieldOptions> _parser = new pb::MessageParser<FieldOptions>(() => new FieldOptions());
     private pb::UnknownFieldSet _unknownFields;
     internal pb::ExtensionSet<FieldOptions> _extensions;
@@ -5750,9 +6395,51 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 8: {
+            Ctype = (global::Google.Protobuf.Reflection.FieldOptions.Types.CType) input.ReadEnum();
+            break;
+          }
+          case 16: {
+            Packed = input.ReadBool();
+            break;
+          }
+          case 24: {
+            Deprecated = input.ReadBool();
+            break;
+          }
+          case 40: {
+            Lazy = input.ReadBool();
+            break;
+          }
+          case 48: {
+            Jstype = (global::Google.Protobuf.Reflection.FieldOptions.Types.JSType) input.ReadEnum();
+            break;
+          }
+          case 80: {
+            Weak = input.ReadBool();
+            break;
+          }
+          case 7994: {
+            uninterpretedOption_.AddEntriesFrom(input, _repeated_uninterpretedOption_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5794,6 +6481,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<FieldOptions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -5850,7 +6538,11 @@
 
   }
 
-  public sealed partial class OneofOptions : pb::IExtendableMessage<OneofOptions>, pb::IBufferMessage {
+  public sealed partial class OneofOptions : pb::IExtendableMessage<OneofOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<OneofOptions> _parser = new pb::MessageParser<OneofOptions>(() => new OneofOptions());
     private pb::UnknownFieldSet _unknownFields;
     internal pb::ExtensionSet<OneofOptions> _extensions;
@@ -5974,9 +6666,27 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 7994: {
+            uninterpretedOption_.AddEntriesFrom(input, _repeated_uninterpretedOption_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -5994,6 +6704,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<OneofOptions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -6019,7 +6730,11 @@
 
   }
 
-  public sealed partial class EnumOptions : pb::IExtendableMessage<EnumOptions>, pb::IBufferMessage {
+  public sealed partial class EnumOptions : pb::IExtendableMessage<EnumOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<EnumOptions> _parser = new pb::MessageParser<EnumOptions>(() => new EnumOptions());
     private pb::UnknownFieldSet _unknownFields;
     internal pb::ExtensionSet<EnumOptions> _extensions;
@@ -6229,9 +6944,35 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 16: {
+            AllowAlias = input.ReadBool();
+            break;
+          }
+          case 24: {
+            Deprecated = input.ReadBool();
+            break;
+          }
+          case 7994: {
+            uninterpretedOption_.AddEntriesFrom(input, _repeated_uninterpretedOption_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6257,6 +6998,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<EnumOptions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -6282,7 +7024,11 @@
 
   }
 
-  public sealed partial class EnumValueOptions : pb::IExtendableMessage<EnumValueOptions>, pb::IBufferMessage {
+  public sealed partial class EnumValueOptions : pb::IExtendableMessage<EnumValueOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<EnumValueOptions> _parser = new pb::MessageParser<EnumValueOptions>(() => new EnumValueOptions());
     private pb::UnknownFieldSet _unknownFields;
     internal pb::ExtensionSet<EnumValueOptions> _extensions;
@@ -6451,9 +7197,31 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 8: {
+            Deprecated = input.ReadBool();
+            break;
+          }
+          case 7994: {
+            uninterpretedOption_.AddEntriesFrom(input, _repeated_uninterpretedOption_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6475,6 +7243,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<EnumValueOptions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -6500,7 +7269,11 @@
 
   }
 
-  public sealed partial class ServiceOptions : pb::IExtendableMessage<ServiceOptions>, pb::IBufferMessage {
+  public sealed partial class ServiceOptions : pb::IExtendableMessage<ServiceOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ServiceOptions> _parser = new pb::MessageParser<ServiceOptions>(() => new ServiceOptions());
     private pb::UnknownFieldSet _unknownFields;
     internal pb::ExtensionSet<ServiceOptions> _extensions;
@@ -6669,9 +7442,31 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 264: {
+            Deprecated = input.ReadBool();
+            break;
+          }
+          case 7994: {
+            uninterpretedOption_.AddEntriesFrom(input, _repeated_uninterpretedOption_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6693,6 +7488,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<ServiceOptions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -6718,7 +7514,11 @@
 
   }
 
-  public sealed partial class MethodOptions : pb::IExtendableMessage<MethodOptions>, pb::IBufferMessage {
+  public sealed partial class MethodOptions : pb::IExtendableMessage<MethodOptions>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<MethodOptions> _parser = new pb::MessageParser<MethodOptions>(() => new MethodOptions());
     private pb::UnknownFieldSet _unknownFields;
     internal pb::ExtensionSet<MethodOptions> _extensions;
@@ -6924,9 +7724,35 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, input)) {
+              _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            }
+            break;
+          case 264: {
+            Deprecated = input.ReadBool();
+            break;
+          }
+          case 272: {
+            IdempotencyLevel = (global::Google.Protobuf.Reflection.MethodOptions.Types.IdempotencyLevel) input.ReadEnum();
+            break;
+          }
+          case 7994: {
+            uninterpretedOption_.AddEntriesFrom(input, _repeated_uninterpretedOption_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -6952,6 +7778,7 @@
         }
       }
     }
+    #endif
 
     public TValue GetExtension<TValue>(pb::Extension<MethodOptions, TValue> extension) {
       return pb::ExtensionSet.Get(ref _extensions, extension);
@@ -7009,7 +7836,11 @@
   /// or produced by Descriptor::CopyTo()) will never have UninterpretedOptions
   /// in them.
   /// </summary>
-  public sealed partial class UninterpretedOption : pb::IMessage<UninterpretedOption>, pb::IBufferMessage {
+  public sealed partial class UninterpretedOption : pb::IMessage<UninterpretedOption>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<UninterpretedOption> _parser = new pb::MessageParser<UninterpretedOption>(() => new UninterpretedOption());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -7339,9 +8170,49 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 18: {
+            name_.AddEntriesFrom(input, _repeated_name_codec);
+            break;
+          }
+          case 26: {
+            IdentifierValue = input.ReadString();
+            break;
+          }
+          case 32: {
+            PositiveIntValue = input.ReadUInt64();
+            break;
+          }
+          case 40: {
+            NegativeIntValue = input.ReadInt64();
+            break;
+          }
+          case 49: {
+            DoubleValue = input.ReadDouble();
+            break;
+          }
+          case 58: {
+            StringValue = input.ReadBytes();
+            break;
+          }
+          case 66: {
+            AggregateValue = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -7381,6 +8252,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the UninterpretedOption message type.</summary>
@@ -7393,7 +8265,11 @@
       /// E.g.,{ ["foo", false], ["bar.baz", true], ["qux", false] } represents
       /// "foo.(bar.baz).qux".
       /// </summary>
-      public sealed partial class NamePart : pb::IMessage<NamePart>, pb::IBufferMessage {
+      public sealed partial class NamePart : pb::IMessage<NamePart>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<NamePart> _parser = new pb::MessageParser<NamePart>(() => new NamePart());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -7557,9 +8433,29 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 10: {
+                NamePart_ = input.ReadString();
+                break;
+              }
+              case 16: {
+                IsExtension = input.ReadBool();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -7579,6 +8475,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -7591,7 +8488,11 @@
   /// Encapsulates information about the original source file from which a
   /// FileDescriptorProto was generated.
   /// </summary>
-  public sealed partial class SourceCodeInfo : pb::IMessage<SourceCodeInfo>, pb::IBufferMessage {
+  public sealed partial class SourceCodeInfo : pb::IMessage<SourceCodeInfo>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<SourceCodeInfo> _parser = new pb::MessageParser<SourceCodeInfo>(() => new SourceCodeInfo());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7741,9 +8642,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            location_.AddEntriesFrom(input, _repeated_location_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -7759,12 +8676,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the SourceCodeInfo message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class Location : pb::IMessage<Location>, pb::IBufferMessage {
+      public sealed partial class Location : pb::IMessage<Location>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<Location> _parser = new pb::MessageParser<Location>(() => new Location());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -8054,9 +8976,43 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 10:
+              case 8: {
+                path_.AddEntriesFrom(input, _repeated_path_codec);
+                break;
+              }
+              case 18:
+              case 16: {
+                span_.AddEntriesFrom(input, _repeated_span_codec);
+                break;
+              }
+              case 26: {
+                LeadingComments = input.ReadString();
+                break;
+              }
+              case 34: {
+                TrailingComments = input.ReadString();
+                break;
+              }
+              case 50: {
+                leadingDetachedComments_.AddEntriesFrom(input, _repeated_leadingDetachedComments_codec);
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -8090,6 +9046,7 @@
             }
           }
         }
+        #endif
 
       }
 
@@ -8103,7 +9060,11 @@
   /// file. A GeneratedCodeInfo message is associated with only one generated
   /// source file, but may contain references to different source .proto files.
   /// </summary>
-  public sealed partial class GeneratedCodeInfo : pb::IMessage<GeneratedCodeInfo>, pb::IBufferMessage {
+  public sealed partial class GeneratedCodeInfo : pb::IMessage<GeneratedCodeInfo>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<GeneratedCodeInfo> _parser = new pb::MessageParser<GeneratedCodeInfo>(() => new GeneratedCodeInfo());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -8212,9 +9173,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            annotation_.AddEntriesFrom(input, _repeated_annotation_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -8230,12 +9207,17 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the GeneratedCodeInfo message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class Annotation : pb::IMessage<Annotation>, pb::IBufferMessage {
+      public sealed partial class Annotation : pb::IMessage<Annotation>
+      #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+          , pb::IBufferMessage
+      #endif
+      {
         private static readonly pb::MessageParser<Annotation> _parser = new pb::MessageParser<Annotation>(() => new Annotation());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -8468,9 +9450,38 @@
 
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public void MergeFrom(pb::CodedInputStream input) {
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
           input.ReadRawMessage(this);
+        #else
+          uint tag;
+          while ((tag = input.ReadTag()) != 0) {
+            switch(tag) {
+              default:
+                _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+                break;
+              case 10:
+              case 8: {
+                path_.AddEntriesFrom(input, _repeated_path_codec);
+                break;
+              }
+              case 18: {
+                SourceFile = input.ReadString();
+                break;
+              }
+              case 24: {
+                Begin = input.ReadInt32();
+                break;
+              }
+              case 32: {
+                End = input.ReadInt32();
+                break;
+              }
+            }
+          }
+        #endif
         }
 
+        #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
           uint tag;
@@ -8499,6 +9510,7 @@
             }
           }
         }
+        #endif
 
       }
 
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs
index c4e7447..fc23560 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs
@@ -119,7 +119,11 @@
   ///       "value": "1.212s"
   ///     }
   /// </summary>
-  public sealed partial class Any : pb::IMessage<Any>, pb::IBufferMessage {
+  public sealed partial class Any : pb::IMessage<Any>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Any> _parser = new pb::MessageParser<Any>(() => new Any());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -288,9 +292,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            TypeUrl = input.ReadString();
+            break;
+          }
+          case 18: {
+            Value = input.ReadBytes();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -310,6 +334,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs
index 1f29224..e8f1a50 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs
@@ -64,7 +64,11 @@
   /// this message itself. See https://cloud.google.com/apis/design/glossary for
   /// detailed terminology.
   /// </summary>
-  public sealed partial class Api : pb::IMessage<Api>, pb::IBufferMessage {
+  public sealed partial class Api : pb::IMessage<Api>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Api> _parser = new pb::MessageParser<Api>(() => new Api());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -341,9 +345,52 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            methods_.AddEntriesFrom(input, _repeated_methods_codec);
+            break;
+          }
+          case 26: {
+            options_.AddEntriesFrom(input, _repeated_options_codec);
+            break;
+          }
+          case 34: {
+            Version = input.ReadString();
+            break;
+          }
+          case 42: {
+            if (sourceContext_ == null) {
+              SourceContext = new global::Google.Protobuf.WellKnownTypes.SourceContext();
+            }
+            input.ReadMessage(SourceContext);
+            break;
+          }
+          case 50: {
+            mixins_.AddEntriesFrom(input, _repeated_mixins_codec);
+            break;
+          }
+          case 56: {
+            Syntax = (global::Google.Protobuf.WellKnownTypes.Syntax) input.ReadEnum();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -386,13 +433,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Method represents a method of an API interface.
   /// </summary>
-  public sealed partial class Method : pb::IMessage<Method>, pb::IBufferMessage {
+  public sealed partial class Method : pb::IMessage<Method>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Method> _parser = new pb::MessageParser<Method>(() => new Method());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -662,9 +714,49 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            RequestTypeUrl = input.ReadString();
+            break;
+          }
+          case 24: {
+            RequestStreaming = input.ReadBool();
+            break;
+          }
+          case 34: {
+            ResponseTypeUrl = input.ReadString();
+            break;
+          }
+          case 40: {
+            ResponseStreaming = input.ReadBool();
+            break;
+          }
+          case 50: {
+            options_.AddEntriesFrom(input, _repeated_options_codec);
+            break;
+          }
+          case 56: {
+            Syntax = (global::Google.Protobuf.WellKnownTypes.Syntax) input.ReadEnum();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -704,6 +796,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -787,7 +880,11 @@
   ///       ...
   ///     }
   /// </summary>
-  public sealed partial class Mixin : pb::IMessage<Mixin>, pb::IBufferMessage {
+  public sealed partial class Mixin : pb::IMessage<Mixin>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Mixin> _parser = new pb::MessageParser<Mixin>(() => new Mixin());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -931,9 +1028,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            Root = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -953,6 +1070,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs
index 804b82f..8ef1b37 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs
@@ -100,7 +100,11 @@
   /// be expressed in JSON format as "3.000000001s", and 3 seconds and 1
   /// microsecond should be expressed in JSON format as "3.000001s".
   /// </summary>
-  public sealed partial class Duration : pb::IMessage<Duration>, pb::IBufferMessage {
+  public sealed partial class Duration : pb::IMessage<Duration>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Duration> _parser = new pb::MessageParser<Duration>(() => new Duration());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -250,9 +254,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Seconds = input.ReadInt64();
+            break;
+          }
+          case 16: {
+            Nanos = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -272,6 +296,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs
index f73c345..ff04940 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs
@@ -50,7 +50,11 @@
   ///
   /// The JSON representation for `Empty` is empty JSON object `{}`.
   /// </summary>
-  public sealed partial class Empty : pb::IMessage<Empty>, pb::IBufferMessage {
+  public sealed partial class Empty : pb::IMessage<Empty>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Empty> _parser = new pb::MessageParser<Empty>(() => new Empty());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -139,9 +143,21 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -153,6 +169,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs b/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs
index 25a2f05..72c049f 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs
@@ -240,7 +240,11 @@
   /// request should verify the included field paths, and return an
   /// `INVALID_ARGUMENT` error if any path is unmappable.
   /// </summary>
-  public sealed partial class FieldMask : pb::IMessage<FieldMask>, pb::IBufferMessage {
+  public sealed partial class FieldMask : pb::IMessage<FieldMask>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FieldMask> _parser = new pb::MessageParser<FieldMask>(() => new FieldMask());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -348,9 +352,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            paths_.AddEntriesFrom(input, _repeated_paths_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -366,6 +386,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs b/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs
index 99d40a5..dbfc8a9 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs
@@ -44,7 +44,11 @@
   /// `SourceContext` represents information about the source of a
   /// protobuf element, like the file in which it is defined.
   /// </summary>
-  public sealed partial class SourceContext : pb::IMessage<SourceContext>, pb::IBufferMessage {
+  public sealed partial class SourceContext : pb::IMessage<SourceContext>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<SourceContext> _parser = new pb::MessageParser<SourceContext>(() => new SourceContext());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -161,9 +165,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            FileName = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -179,6 +199,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs
index 8405742..2ba1b1c 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs
@@ -77,7 +77,11 @@
   ///
   /// The JSON representation for `Struct` is JSON object.
   /// </summary>
-  public sealed partial class Struct : pb::IMessage<Struct>, pb::IBufferMessage {
+  public sealed partial class Struct : pb::IMessage<Struct>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Struct> _parser = new pb::MessageParser<Struct>(() => new Struct());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -185,9 +189,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            fields_.AddEntriesFrom(input, _map_fields_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -203,6 +223,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -214,7 +235,11 @@
   ///
   /// The JSON representation for `Value` is JSON value.
   /// </summary>
-  public sealed partial class Value : pb::IMessage<Value>, pb::IBufferMessage {
+  public sealed partial class Value : pb::IMessage<Value>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Value> _parser = new pb::MessageParser<Value>(() => new Value());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -514,9 +539,56 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            kind_ = input.ReadEnum();
+            kindCase_ = KindOneofCase.NullValue;
+            break;
+          }
+          case 17: {
+            NumberValue = input.ReadDouble();
+            break;
+          }
+          case 26: {
+            StringValue = input.ReadString();
+            break;
+          }
+          case 32: {
+            BoolValue = input.ReadBool();
+            break;
+          }
+          case 42: {
+            global::Google.Protobuf.WellKnownTypes.Struct subBuilder = new global::Google.Protobuf.WellKnownTypes.Struct();
+            if (kindCase_ == KindOneofCase.StructValue) {
+              subBuilder.MergeFrom(StructValue);
+            }
+            input.ReadMessage(subBuilder);
+            StructValue = subBuilder;
+            break;
+          }
+          case 50: {
+            global::Google.Protobuf.WellKnownTypes.ListValue subBuilder = new global::Google.Protobuf.WellKnownTypes.ListValue();
+            if (kindCase_ == KindOneofCase.ListValue) {
+              subBuilder.MergeFrom(ListValue);
+            }
+            input.ReadMessage(subBuilder);
+            ListValue = subBuilder;
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -563,6 +635,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -571,7 +644,11 @@
   ///
   /// The JSON representation for `ListValue` is JSON array.
   /// </summary>
-  public sealed partial class ListValue : pb::IMessage<ListValue>, pb::IBufferMessage {
+  public sealed partial class ListValue : pb::IMessage<ListValue>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<ListValue> _parser = new pb::MessageParser<ListValue>(() => new ListValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -679,9 +756,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            values_.AddEntriesFrom(input, _repeated_values_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -697,6 +790,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs
index 31cbe95..208cd26 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs
@@ -123,7 +123,11 @@
   /// http://www.joda.org/joda-time/apidocs/org/joda/time/format/ISODateTimeFormat.html#dateTime%2D%2D
   /// ) to obtain a formatter capable of generating timestamps in this format.
   /// </summary>
-  public sealed partial class Timestamp : pb::IMessage<Timestamp>, pb::IBufferMessage {
+  public sealed partial class Timestamp : pb::IMessage<Timestamp>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Timestamp> _parser = new pb::MessageParser<Timestamp>(() => new Timestamp());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -271,9 +275,29 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Seconds = input.ReadInt64();
+            break;
+          }
+          case 16: {
+            Nanos = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -293,6 +317,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs
index 3c074f8..453ff8d 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs
@@ -94,7 +94,11 @@
   /// <summary>
   /// A protocol buffer message type.
   /// </summary>
-  public sealed partial class Type : pb::IMessage<Type>, pb::IBufferMessage {
+  public sealed partial class Type : pb::IMessage<Type>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Type> _parser = new pb::MessageParser<Type>(() => new Type());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -324,9 +328,48 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            fields_.AddEntriesFrom(input, _repeated_fields_codec);
+            break;
+          }
+          case 26: {
+            oneofs_.AddEntriesFrom(input, _repeated_oneofs_codec);
+            break;
+          }
+          case 34: {
+            options_.AddEntriesFrom(input, _repeated_options_codec);
+            break;
+          }
+          case 42: {
+            if (sourceContext_ == null) {
+              SourceContext = new global::Google.Protobuf.WellKnownTypes.SourceContext();
+            }
+            input.ReadMessage(SourceContext);
+            break;
+          }
+          case 48: {
+            Syntax = (global::Google.Protobuf.WellKnownTypes.Syntax) input.ReadEnum();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -365,13 +408,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// A single field of a message type.
   /// </summary>
-  public sealed partial class Field : pb::IMessage<Field>, pb::IBufferMessage {
+  public sealed partial class Field : pb::IMessage<Field>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Field> _parser = new pb::MessageParser<Field>(() => new Field());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -724,9 +772,61 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Kind = (global::Google.Protobuf.WellKnownTypes.Field.Types.Kind) input.ReadEnum();
+            break;
+          }
+          case 16: {
+            Cardinality = (global::Google.Protobuf.WellKnownTypes.Field.Types.Cardinality) input.ReadEnum();
+            break;
+          }
+          case 24: {
+            Number = input.ReadInt32();
+            break;
+          }
+          case 34: {
+            Name = input.ReadString();
+            break;
+          }
+          case 50: {
+            TypeUrl = input.ReadString();
+            break;
+          }
+          case 56: {
+            OneofIndex = input.ReadInt32();
+            break;
+          }
+          case 64: {
+            Packed = input.ReadBool();
+            break;
+          }
+          case 74: {
+            options_.AddEntriesFrom(input, _repeated_options_codec);
+            break;
+          }
+          case 82: {
+            JsonName = input.ReadString();
+            break;
+          }
+          case 90: {
+            DefaultValue = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -778,6 +878,7 @@
         }
       }
     }
+    #endif
 
     #region Nested types
     /// <summary>Container for nested types declared in the Field message type.</summary>
@@ -895,7 +996,11 @@
   /// <summary>
   /// Enum type definition.
   /// </summary>
-  public sealed partial class Enum : pb::IMessage<Enum>, pb::IBufferMessage {
+  public sealed partial class Enum : pb::IMessage<Enum>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Enum> _parser = new pb::MessageParser<Enum>(() => new Enum());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1106,9 +1211,44 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            enumvalue_.AddEntriesFrom(input, _repeated_enumvalue_codec);
+            break;
+          }
+          case 26: {
+            options_.AddEntriesFrom(input, _repeated_options_codec);
+            break;
+          }
+          case 34: {
+            if (sourceContext_ == null) {
+              SourceContext = new global::Google.Protobuf.WellKnownTypes.SourceContext();
+            }
+            input.ReadMessage(SourceContext);
+            break;
+          }
+          case 40: {
+            Syntax = (global::Google.Protobuf.WellKnownTypes.Syntax) input.ReadEnum();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1143,13 +1283,18 @@
         }
       }
     }
+    #endif
 
   }
 
   /// <summary>
   /// Enum value definition.
   /// </summary>
-  public sealed partial class EnumValue : pb::IMessage<EnumValue>, pb::IBufferMessage {
+  public sealed partial class EnumValue : pb::IMessage<EnumValue>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<EnumValue> _parser = new pb::MessageParser<EnumValue>(() => new EnumValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1311,9 +1456,33 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 16: {
+            Number = input.ReadInt32();
+            break;
+          }
+          case 26: {
+            options_.AddEntriesFrom(input, _repeated_options_codec);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1337,6 +1506,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -1344,7 +1514,11 @@
   /// A protocol buffer option, which can be attached to a message, field,
   /// enumeration, etc.
   /// </summary>
-  public sealed partial class Option : pb::IMessage<Option>, pb::IBufferMessage {
+  public sealed partial class Option : pb::IMessage<Option>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Option> _parser = new pb::MessageParser<Option>(() => new Option());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1496,9 +1670,32 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Name = input.ReadString();
+            break;
+          }
+          case 18: {
+            if (value_ == null) {
+              Value = new global::Google.Protobuf.WellKnownTypes.Any();
+            }
+            input.ReadMessage(Value);
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1521,6 +1718,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
index 41313fc..fa3458c 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
@@ -57,7 +57,11 @@
   ///
   /// The JSON representation for `DoubleValue` is JSON number.
   /// </summary>
-  public sealed partial class DoubleValue : pb::IMessage<DoubleValue>, pb::IBufferMessage {
+  public sealed partial class DoubleValue : pb::IMessage<DoubleValue>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<DoubleValue> _parser = new pb::MessageParser<DoubleValue>(() => new DoubleValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -173,9 +177,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 9: {
+            Value = input.ReadDouble();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -191,6 +211,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -199,7 +220,11 @@
   ///
   /// The JSON representation for `FloatValue` is JSON number.
   /// </summary>
-  public sealed partial class FloatValue : pb::IMessage<FloatValue>, pb::IBufferMessage {
+  public sealed partial class FloatValue : pb::IMessage<FloatValue>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<FloatValue> _parser = new pb::MessageParser<FloatValue>(() => new FloatValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -315,9 +340,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 13: {
+            Value = input.ReadFloat();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -333,6 +374,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -341,7 +383,11 @@
   ///
   /// The JSON representation for `Int64Value` is JSON string.
   /// </summary>
-  public sealed partial class Int64Value : pb::IMessage<Int64Value>, pb::IBufferMessage {
+  public sealed partial class Int64Value : pb::IMessage<Int64Value>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Int64Value> _parser = new pb::MessageParser<Int64Value>(() => new Int64Value());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -457,9 +503,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Value = input.ReadInt64();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -475,6 +537,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -483,7 +546,11 @@
   ///
   /// The JSON representation for `UInt64Value` is JSON string.
   /// </summary>
-  public sealed partial class UInt64Value : pb::IMessage<UInt64Value>, pb::IBufferMessage {
+  public sealed partial class UInt64Value : pb::IMessage<UInt64Value>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<UInt64Value> _parser = new pb::MessageParser<UInt64Value>(() => new UInt64Value());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -599,9 +666,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Value = input.ReadUInt64();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -617,6 +700,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -625,7 +709,11 @@
   ///
   /// The JSON representation for `Int32Value` is JSON number.
   /// </summary>
-  public sealed partial class Int32Value : pb::IMessage<Int32Value>, pb::IBufferMessage {
+  public sealed partial class Int32Value : pb::IMessage<Int32Value>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<Int32Value> _parser = new pb::MessageParser<Int32Value>(() => new Int32Value());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -741,9 +829,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Value = input.ReadInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -759,6 +863,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -767,7 +872,11 @@
   ///
   /// The JSON representation for `UInt32Value` is JSON number.
   /// </summary>
-  public sealed partial class UInt32Value : pb::IMessage<UInt32Value>, pb::IBufferMessage {
+  public sealed partial class UInt32Value : pb::IMessage<UInt32Value>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<UInt32Value> _parser = new pb::MessageParser<UInt32Value>(() => new UInt32Value());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -883,9 +992,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Value = input.ReadUInt32();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -901,6 +1026,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -909,7 +1035,11 @@
   ///
   /// The JSON representation for `BoolValue` is JSON `true` and `false`.
   /// </summary>
-  public sealed partial class BoolValue : pb::IMessage<BoolValue>, pb::IBufferMessage {
+  public sealed partial class BoolValue : pb::IMessage<BoolValue>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<BoolValue> _parser = new pb::MessageParser<BoolValue>(() => new BoolValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1025,9 +1155,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 8: {
+            Value = input.ReadBool();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1043,6 +1189,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -1051,7 +1198,11 @@
   ///
   /// The JSON representation for `StringValue` is JSON string.
   /// </summary>
-  public sealed partial class StringValue : pb::IMessage<StringValue>, pb::IBufferMessage {
+  public sealed partial class StringValue : pb::IMessage<StringValue>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<StringValue> _parser = new pb::MessageParser<StringValue>(() => new StringValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1167,9 +1318,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Value = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1185,6 +1352,7 @@
         }
       }
     }
+    #endif
 
   }
 
@@ -1193,7 +1361,11 @@
   ///
   /// The JSON representation for `BytesValue` is JSON string.
   /// </summary>
-  public sealed partial class BytesValue : pb::IMessage<BytesValue>, pb::IBufferMessage {
+  public sealed partial class BytesValue : pb::IMessage<BytesValue>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
     private static readonly pb::MessageParser<BytesValue> _parser = new pb::MessageParser<BytesValue>(() => new BytesValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1309,9 +1481,25 @@
 
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
       input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            Value = input.ReadBytes();
+            break;
+          }
+        }
+      }
+    #endif
     }
 
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
       uint tag;
@@ -1327,6 +1515,7 @@
         }
       }
     }
+    #endif
 
   }
 
diff --git a/docs/third_party.md b/docs/third_party.md
index 11a6efb..257f9d5 100644
--- a/docs/third_party.md
+++ b/docs/third_party.md
@@ -18,6 +18,7 @@
 * C: https://github.com/squidfunk/protobluff
 * C: https://github.com/eerimoq/pbtools
 * C++: https://github.com/google/protobuf (Google-official implementation)
+* C++: https://EmbeddedProto.com
 * C/C++: http://spbc.sf.net/
 * C#: http://code.google.com/p/protobuf-csharp-port
 * C#: https://silentorbit.com/protobuf/
diff --git a/java/bom/pom.xml b/java/bom/pom.xml
index 5a63a1d..ff2d106 100644
--- a/java/bom/pom.xml
+++ b/java/bom/pom.xml
@@ -4,7 +4,7 @@
 
   <groupId>com.google.protobuf</groupId>
   <artifactId>protobuf-bom</artifactId>
-  <version>3.12.2</version>
+  <version>3.12.3</version>
   <packaging>pom</packaging>
 
   <name>Protocol Buffers [BOM]</name>
diff --git a/java/core/pom.xml b/java/core/pom.xml
index 4112eb2..b2b0b03 100644
--- a/java/core/pom.xml
+++ b/java/core/pom.xml
@@ -4,7 +4,7 @@
   <parent>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-parent</artifactId>
-    <version>3.12.2</version>
+    <version>3.12.3</version>
   </parent>
 
   <artifactId>protobuf-java</artifactId>
diff --git a/java/lite/pom.xml b/java/lite/pom.xml
index 30e6f37..49686cd 100644
--- a/java/lite/pom.xml
+++ b/java/lite/pom.xml
@@ -4,7 +4,7 @@
   <parent>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-parent</artifactId>
-    <version>3.12.2</version>
+    <version>3.12.3</version>
   </parent>
 
   <artifactId>protobuf-javalite</artifactId>
diff --git a/java/pom.xml b/java/pom.xml
index f61c857..0a813e0 100644
--- a/java/pom.xml
+++ b/java/pom.xml
@@ -4,7 +4,7 @@
 
   <groupId>com.google.protobuf</groupId>
   <artifactId>protobuf-parent</artifactId>
-  <version>3.12.2</version>
+  <version>3.12.3</version>
   <packaging>pom</packaging>
 
   <name>Protocol Buffers [Parent]</name>
diff --git a/java/util/pom.xml b/java/util/pom.xml
index a9b8b4a..daa123a 100644
--- a/java/util/pom.xml
+++ b/java/util/pom.xml
@@ -4,7 +4,7 @@
   <parent>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-parent</artifactId>
-    <version>3.12.2</version>
+    <version>3.12.3</version>
   </parent>
 
   <artifactId>protobuf-java-util</artifactId>
diff --git a/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java b/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java
index d07731d..4092b30 100644
--- a/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java
+++ b/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java
@@ -30,6 +30,7 @@
 
 package com.google.protobuf.util;
 
+import com.google.common.base.Splitter;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.protobuf.Descriptors.Descriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
@@ -66,7 +67,7 @@
   private static final String FIELD_PATH_SEPARATOR_REGEX = "\\.";
 
   private static final class Node {
-    final SortedMap<String, Node> children = new TreeMap<String, Node>();
+    final SortedMap<String, Node> children = new TreeMap<>();
   }
 
   private final Node root = new Node();
@@ -97,6 +98,7 @@
    * to add is a sub-path of an existing leaf node, nothing will be changed in the tree.
    */
   @CanIgnoreReturnValue
+  @SuppressWarnings("StringSplitter")
   FieldMaskTree addFieldPath(String path) {
     String[] parts = path.split(FIELD_PATH_SEPARATOR_REGEX);
     if (parts.length == 0) {
@@ -135,13 +137,52 @@
   }
 
   /**
+   * Remove {@code path} from the tree.
+   *
+   * <p>When removing a field path from the tree, all sub-paths will be removed. That is, after
+   * removing "foo.bar" from the tree, "foo.bar.baz" will be removed. Likewise, if the field path to
+   * remove is a non-exist sub-path, nothing will be changed.
+   */
+  @CanIgnoreReturnValue
+  FieldMaskTree removeFieldPath(String path) {
+    List<String> parts = Splitter.onPattern(FIELD_PATH_SEPARATOR_REGEX).splitToList(path);
+    if (parts.isEmpty()) {
+      return this;
+    }
+    Node node = root;
+    for (int i = 0; i < parts.size(); i++) {
+      String key = parts.get(i);
+      if (!node.children.containsKey(key)) {
+        // Path does not exist.
+        return this;
+      }
+      if (i == parts.size() - 1) {
+        // Remove path.
+        node.children.remove(key);
+        return this;
+      }
+      node = node.children.get(key);
+    }
+    return this;
+  }
+
+  /** Removes all field paths in {@code mask} from this tree. */
+  @CanIgnoreReturnValue
+  FieldMaskTree removeFromFieldMask(FieldMask mask) {
+    for (String path : mask.getPathsList()) {
+      removeFieldPath(path);
+    }
+    return this;
+  }
+
+  /**
    * Converts this tree to a FieldMask.
    */
   FieldMask toFieldMask() {
     if (root.children.isEmpty()) {
       return FieldMask.getDefaultInstance();
     }
-    List<String> paths = new ArrayList<String>();
+    List<String> paths = new ArrayList<>();
     getFieldPaths(root, "", paths);
     return FieldMask.newBuilder().addAllPaths(paths).build();
   }
@@ -186,7 +227,7 @@
     }
     // We found a matching node for the path. All leaf children of this matching
     // node is in the intersection.
-    List<String> paths = new ArrayList<String>();
+    List<String> paths = new ArrayList<>();
     getFieldPaths(node, path, paths);
     for (String value : paths) {
       output.addFieldPath(value);
diff --git a/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java b/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java
index 312d30f..0c2f90c 100644
--- a/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java
+++ b/java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java
@@ -276,6 +276,16 @@
     return maskTree.toFieldMask();
   }
 
+  /** Subtracts {@code secondMask} and {@code otherMasks} from {@code firstMask}. */
+  public static FieldMask subtract(
+      FieldMask firstMask, FieldMask secondMask, FieldMask... otherMasks) {
+    FieldMaskTree maskTree = new FieldMaskTree(firstMask).removeFromFieldMask(secondMask);
+    for (FieldMask mask : otherMasks) {
+      maskTree.removeFromFieldMask(mask);
+    }
+    return maskTree.toFieldMask();
+  }
+
   /**
    * Calculates the intersection of two FieldMasks.
    */
diff --git a/java/util/src/test/java/com/google/protobuf/util/FieldMaskTreeTest.java b/java/util/src/test/java/com/google/protobuf/util/FieldMaskTreeTest.java
index baae224..7ec37d0 100644
--- a/java/util/src/test/java/com/google/protobuf/util/FieldMaskTreeTest.java
+++ b/java/util/src/test/java/com/google/protobuf/util/FieldMaskTreeTest.java
@@ -30,6 +30,8 @@
 
 package com.google.protobuf.util;
 
+import static com.google.common.truth.Truth.assertThat;
+
 import com.google.protobuf.DynamicMessage;
 import com.google.protobuf.Message;
 import com.google.protobuf.UninitializedMessageException;
@@ -43,9 +45,9 @@
 public class FieldMaskTreeTest extends TestCase {
   public void testAddFieldPath() throws Exception {
     FieldMaskTree tree = new FieldMaskTree();
-    assertEquals("", tree.toString());
+    assertThat(tree.toString()).isEmpty();
     tree.addFieldPath("");
-    assertEquals("", tree.toString());
+    assertThat(tree.toString()).isEmpty();
     // New branch.
     tree.addFieldPath("foo");
     assertEquals("foo", tree.toString());
@@ -73,15 +75,45 @@
     assertEquals("bar,foo", tree.toString());
   }
 
+  public void testRemoveFieldPath() throws Exception {
+    String initialTreeString = "bar.baz,bar.quz.bar,foo";
+    FieldMaskTree tree = new FieldMaskTree(FieldMaskUtil.fromString(initialTreeString));
+    // Empty path.
+    tree.removeFieldPath("");
+    assertEquals(initialTreeString, tree.toString());
+    // Non-exist sub-path of an existing leaf.
+    tree.removeFieldPath("foo.bar");
+    assertEquals(initialTreeString, tree.toString());
+    // Non-exist path.
+    tree.removeFieldPath("bar.foo");
+    assertEquals(initialTreeString, tree.toString());
+    // Match an existing leaf node.
+    tree.removeFieldPath("foo");
+    assertEquals("bar.baz,bar.quz.bar", tree.toString());
+    // Match sub-path of an existing leaf node.
+    tree.removeFieldPath("bar.quz.bar");
+    assertEquals("bar.baz,bar.quz", tree.toString());
+    // Match a non-leaf node.
+    tree.removeFieldPath("bar");
+    assertThat(tree.toString()).isEmpty();
+  }
+
+  public void testRemoveFromFieldMask() throws Exception {
+    FieldMaskTree tree = new FieldMaskTree(FieldMaskUtil.fromString("foo,bar.baz,bar.quz"));
+    assertEquals("bar.baz,bar.quz,foo", tree.toString());
+    tree.removeFromFieldMask(FieldMaskUtil.fromString("foo.bar,bar"));
+    assertEquals("foo", tree.toString());
+  }
+
   public void testIntersectFieldPath() throws Exception {
     FieldMaskTree tree = new FieldMaskTree(FieldMaskUtil.fromString("foo,bar.baz,bar.quz"));
     FieldMaskTree result = new FieldMaskTree();
     // Empty path.
     tree.intersectFieldPath("", result);
-    assertEquals("", result.toString());
+    assertThat(result.toString()).isEmpty();
     // Non-exist path.
     tree.intersectFieldPath("quz", result);
-    assertEquals("", result.toString());
+    assertThat(result.toString()).isEmpty();
     // Sub-path of an existing leaf.
     tree.intersectFieldPath("foo.bar", result);
     assertEquals("foo.bar", result.toString());
diff --git a/java/util/src/test/java/com/google/protobuf/util/FieldMaskUtilTest.java b/java/util/src/test/java/com/google/protobuf/util/FieldMaskUtilTest.java
index 78b470e..796020e 100644
--- a/java/util/src/test/java/com/google/protobuf/util/FieldMaskUtilTest.java
+++ b/java/util/src/test/java/com/google/protobuf/util/FieldMaskUtilTest.java
@@ -224,6 +224,24 @@
     assertEquals("bar,foo", FieldMaskUtil.toString(result));
   }
 
+  public void testSubstract() throws Exception {
+    // Only test a simple case here and expect
+    // {@link FieldMaskTreeTest#testRemoveFieldPath} to cover all scenarios.
+    FieldMask mask1 = FieldMaskUtil.fromString("foo,bar.baz,bar.quz");
+    FieldMask mask2 = FieldMaskUtil.fromString("foo.bar,bar");
+    FieldMask result = FieldMaskUtil.subtract(mask1, mask2);
+    assertEquals("foo", FieldMaskUtil.toString(result));
+  }
+
+  public void testSubstract_usingVarArgs() throws Exception {
+    FieldMask mask1 = FieldMaskUtil.fromString("foo,bar.baz,bar.quz.bar");
+    FieldMask mask2 = FieldMaskUtil.fromString("foo.bar,bar.baz.quz");
+    FieldMask mask3 = FieldMaskUtil.fromString("bar.quz");
+    FieldMask mask4 = FieldMaskUtil.fromString("foo,bar.baz");
+    FieldMask result = FieldMaskUtil.subtract(mask1, mask2, mask3, mask4);
+    assertEquals("bar", FieldMaskUtil.toString(result));
+  }
+
   public void testIntersection() throws Exception {
     // Only test a simple case here and expect
     // {@link FieldMaskTreeTest#testIntersectFieldPath} to cover all scenarios.
diff --git a/kokoro/macos/objectivec_cocoapods_integration/build.sh b/kokoro/macos/objectivec_cocoapods_integration/build.sh
index f96d289..8f3c9b4 100755
--- a/kokoro/macos/objectivec_cocoapods_integration/build.sh
+++ b/kokoro/macos/objectivec_cocoapods_integration/build.sh
@@ -6,6 +6,7 @@
 cd $(dirname $0)/../../..
 
 # Prepare worker environment to run tests
+KOKORO_INSTALL_COCOAPODS=yes
 source kokoro/macos/prepare_build_macos_rc
 
 ./tests.sh objectivec_cocoapods_integration
diff --git a/kokoro/macos/prepare_build_macos_rc b/kokoro/macos/prepare_build_macos_rc
index 2428750..18ce60b 100755
--- a/kokoro/macos/prepare_build_macos_rc
+++ b/kokoro/macos/prepare_build_macos_rc
@@ -2,6 +2,8 @@
 #
 # This script sets up a Kokoro MacOS worker for running Protobuf tests
 
+set -eux
+
 ##
 # Select Xcode version
 
@@ -18,24 +20,61 @@
 export CXX=g++
 
 ##
-# Install Brew and core softwares
+# Brew: update, then upgrade the installed tools to current version and install
+# some needed ones not in the Kokoro base image. This ensure current versions
+# of CMake, autotools, etc.
 
-ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
-source $HOME/.rvm/scripts/rvm
-brew uninstall node icu4c cmake wget
-brew prune
-brew install gflags gpg gpg2 node openssl pcre ruby cmake wget
-sudo chown -R $(whoami) /usr/local
-brew postinstall node
+# But first...
+#
+# The transitive deps of the installed tools need protobuf, but Kokoro manually
+# installed it outside of brew so it needs to be removed so brew can install the
+# tools (and a newer version of protobuf). g/kokoro-users/7FRvQMUdN40 about why
+# it is a manual install vs. a brew install in the first place.
+sudo rm -rf \
+    /usr/local/include/google/protobuf \
+    /usr/local/bin/protoc
+# Likewise, updating python can have issues because of some existing binaries.
+sudo rm -rf \
+    /usr/local/bin/2to3* \
+    /usr/local/bin/idle3* \
+    /usr/local/bin/pydoc3* \
+    /usr/local/bin/python3* \
+    /usr/local/bin/pyvenv*
+
+brew update
+brew upgrade
+
+##
+# Install Ruby
+
+if [[ "${KOKORO_INSTALL_RUBY:-}" == "yes" ]] ; then
+  brew install ruby
+fi
+
+##
+# Install Cocoapods
+
+if [[ "${KOKORO_INSTALL_COCOAPODS:-}" == "yes" ]] ; then
+  # The existing cocoapods was installed via gem, but that doesn't work well
+  # with the overlap in deps with things managed by brew (errors around ruby
+  # versions, etc.); so remove it and install in via brew instead.
+  gem uninstall -a "$(gem list | grep cocoapods | cut -d ' ' -f 1)"
+  brew install cocoapods
+fi
 
 ##
 # Install Tox
 
-sudo pip install tox==2.4.1
+if [[ "${KOKORO_INSTALL_TOX:-}" == "yes" ]] ; then
+  sudo pip install tox==2.4.1
+fi
 
 ##
 # Install RVM
 
-gpg2 --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3
-command curl -sSL https://rvm.io/mpapis.asc | gpg2 --import -
-curl -sSL https://get.rvm.io | bash -s stable --ruby
+if [[ "${KOKORO_INSTALL_RVM:-}" == "yes" ]] ; then
+  curl -sSL https://rvm.io/mpapis.asc | gpg --import -
+  curl -sSL https://rvm.io/pkuczynski.asc | gpg --import -
+
+  curl -sSL https://get.rvm.io | bash -s stable --ruby
+fi
diff --git a/kokoro/macos/python/build.sh b/kokoro/macos/python/build.sh
index 6b17b95..388e24b 100755
--- a/kokoro/macos/python/build.sh
+++ b/kokoro/macos/python/build.sh
@@ -6,6 +6,7 @@
 cd $(dirname $0)/../../..
 
 # Prepare worker environment to run tests
+KOKORO_INSTALL_TOX=yes
 source kokoro/macos/prepare_build_macos_rc
 
 ./tests.sh python
diff --git a/kokoro/macos/python_cpp/build.sh b/kokoro/macos/python_cpp/build.sh
index cb53def..f86dd6f 100755
--- a/kokoro/macos/python_cpp/build.sh
+++ b/kokoro/macos/python_cpp/build.sh
@@ -6,6 +6,7 @@
 cd $(dirname $0)/../../..
 
 # Prepare worker environment to run tests
+KOKORO_INSTALL_TOX=yes
 source kokoro/macos/prepare_build_macos_rc
 g++ --version
 
diff --git a/kokoro/macos/ruby23/build.sh b/kokoro/macos/ruby23/build.sh
index dc950a2..9317838 100755
--- a/kokoro/macos/ruby23/build.sh
+++ b/kokoro/macos/ruby23/build.sh
@@ -6,6 +6,8 @@
 cd $(dirname $0)/../../..
 
 # Prepare worker environment to run tests
+KOKORO_INSTALL_RUBY=yes
+KOKORO_INSTALL_RVM=yes
 source kokoro/macos/prepare_build_macos_rc
 
 ./tests.sh ruby23
diff --git a/kokoro/macos/ruby24/build.sh b/kokoro/macos/ruby24/build.sh
index 3c3a190..51bb2e6 100755
--- a/kokoro/macos/ruby24/build.sh
+++ b/kokoro/macos/ruby24/build.sh
@@ -6,6 +6,8 @@
 cd $(dirname $0)/../../..
 
 # Prepare worker environment to run tests
+KOKORO_INSTALL_RUBY=yes
+KOKORO_INSTALL_RVM=yes
 source kokoro/macos/prepare_build_macos_rc
 
 ./tests.sh ruby24
diff --git a/kokoro/macos/ruby25/build.sh b/kokoro/macos/ruby25/build.sh
index 38e90aa..ba2d0a4 100755
--- a/kokoro/macos/ruby25/build.sh
+++ b/kokoro/macos/ruby25/build.sh
@@ -6,6 +6,8 @@
 cd $(dirname $0)/../../..
 
 # Prepare worker environment to run tests
+KOKORO_INSTALL_RUBY=yes
+KOKORO_INSTALL_RVM=yes
 source kokoro/macos/prepare_build_macos_rc
 
 ./tests.sh ruby25
diff --git a/kokoro/macos/ruby26/build.sh b/kokoro/macos/ruby26/build.sh
index 6c33ed0..5a4c243 100755
--- a/kokoro/macos/ruby26/build.sh
+++ b/kokoro/macos/ruby26/build.sh
@@ -6,6 +6,8 @@
 cd $(dirname $0)/../../..
 
 # Prepare worker environment to run tests
+KOKORO_INSTALL_RUBY=yes
+KOKORO_INSTALL_RVM=yes
 source kokoro/macos/prepare_build_macos_rc
 
 ./tests.sh ruby26
diff --git a/kokoro/macos/ruby27/build.sh b/kokoro/macos/ruby27/build.sh
index 16bcbd6..b1529b9 100755
--- a/kokoro/macos/ruby27/build.sh
+++ b/kokoro/macos/ruby27/build.sh
@@ -6,6 +6,8 @@
 cd $(dirname $0)/../../..
 
 # Prepare worker environment to run tests
+KOKORO_INSTALL_RUBY=yes
+KOKORO_INSTALL_RVM=yes
 source kokoro/macos/prepare_build_macos_rc
 
 ./tests.sh ruby27
diff --git a/objectivec/GPBDescriptor_PackagePrivate.h b/objectivec/GPBDescriptor_PackagePrivate.h
index b3d6730..408f8d4 100644
--- a/objectivec/GPBDescriptor_PackagePrivate.h
+++ b/objectivec/GPBDescriptor_PackagePrivate.h
@@ -131,14 +131,29 @@
 typedef struct GPBExtensionDescription {
   GPBGenericValue defaultValue;
   const char *singletonName;
+  // Before 3.12, `extendedClass` was just a `const char *`. Thanks to nested
+  // initialization (https://en.cppreference.com/w/c/language/struct_initialization#Nested_initialization)
+  // old generated code with `.extendedClass = GPBStringifySymbol(Something)`
+  // still works; and the current generator can use `extendedClass.clazz`, to
+  // pass a Class reference.
   union {
     const char *name;
     Class clazz;
   } extendedClass;
+  // Before 3.12, this was `const char *messageOrGroupClassName`. In the
+  // initial 3.12 release, we moved the `union messageOrGroupClass`, and failed
+  // to realize that would break existing source code for extensions. So to
+  // keep existing source code working, we added an unnamed union (C11) to
+  // provide both the old field name and the new union. This keeps both older
+  // and newer code working.
+  // Background: https://github.com/protocolbuffers/protobuf/issues/7555
   union {
-    const char *name;
-    Class clazz;
-  } messageOrGroupClass;
+    const char *messageOrGroupClassName;
+    union {
+     const char *name;
+     Class clazz;
+   } messageOrGroupClass;
+  };
   GPBEnumDescriptorFunc enumDescriptorFunc;
   int32_t fieldNumber;
   GPBDataType dataType;
diff --git a/objectivec/README.md b/objectivec/README.md
index 69fe631..5982939 100644
--- a/objectivec/README.md
+++ b/objectivec/README.md
@@ -172,6 +172,12 @@
     lot of proto files included in it; and having multiple lines makes things
     easier to read.
 
+  * `runtime_import_prefix`: The `value` used for this key to be used as a
+    prefix on `#import`s of runtime provided headers in the generated files.
+    When integrating ObjC protos into a build system, this can be used to avoid
+    having to add the runtime directory to the header search path since the
+    generate `#import` will be more complete.
+
 Contributing
 ------------
 
diff --git a/php/composer.json b/php/composer.json
index b618ea1..abcc293 100644
--- a/php/composer.json
+++ b/php/composer.json
@@ -23,7 +23,7 @@
     }
   },
   "scripts": {
-    "test": "(cd tests && rm -rf generated && mkdir -p generated && ../../src/protoc --php_out=generated -I../../src -I. proto/empty/echo.proto proto/test.proto proto/test_include.proto proto/test_no_namespace.proto proto/test_prefix.proto proto/test_php_namespace.proto proto/test_empty_php_namespace.proto proto/test_reserved_enum_lower.proto proto/test_reserved_enum_upper.proto proto/test_reserved_enum_value_lower.proto proto/test_reserved_enum_value_upper.proto proto/test_reserved_message_lower.proto proto/test_reserved_message_upper.proto proto/test_service.proto proto/test_service_namespace.proto proto/test_wrapper_type_setters.proto proto/test_descriptors.proto) && (cd ../src && ./protoc --php_out=../php/tests/generated -I../php/tests -I. ../php/tests/proto/test_import_descriptor_proto.proto) && vendor/bin/phpunit",
-    "aggregate_metadata_test": "(cd tests && rm -rf generated && mkdir -p generated && ../../src/protoc --php_out=aggregate_metadata=foo#bar:generated -I../../src -I. proto/test.proto proto/test_include.proto && ../../src/protoc --php_out=generated -I../../src -I. proto/empty/echo.proto proto/test_no_namespace.proto proto/test_empty_php_namespace.proto proto/test_prefix.proto proto/test_php_namespace.proto proto/test_reserved_enum_lower.proto proto/test_reserved_enum_upper.proto proto/test_reserved_enum_value_lower.proto proto/test_reserved_enum_value_upper.proto proto/test_reserved_message_lower.proto proto/test_reserved_message_upper.proto proto/test_service.proto proto/test_service_namespace.proto proto/test_wrapper_type_setters.proto proto/test_descriptors.proto) && (cd ../src && ./protoc --php_out=aggregate_metadata=foo:../php/tests/generated -I../php/tests -I. ../php/tests/proto/test_import_descriptor_proto.proto) && vendor/bin/phpunit"
+    "test": "tests/generate_protos.sh && vendor/bin/phpunit",
+    "aggregate_metadata_test": "tests/generate_protos.sh --aggregate_metadata && vendor/bin/phpunit"
   }
 }
diff --git a/php/ext/google/protobuf/message.c b/php/ext/google/protobuf/message.c
index e8d4c6f..0366337 100644
--- a/php/ext/google/protobuf/message.c
+++ b/php/ext/google/protobuf/message.c
@@ -1726,7 +1726,7 @@
                              0 ,ZEND_ACC_PRIVATE TSRMLS_CC);
 PHP_PROTO_INIT_SUBMSGCLASS_END
 
-PHP_METHOD(Timestamp, __construct) {
+static PHP_METHOD(Timestamp, __construct) {
   init_file_timestamp(TSRMLS_C);
   INIT_MESSAGE_WITH_ARRAY;
 }
diff --git a/php/ext/google/protobuf/package.xml b/php/ext/google/protobuf/package.xml
index 5c9d810..01a4b86 100644
--- a/php/ext/google/protobuf/package.xml
+++ b/php/ext/google/protobuf/package.xml
@@ -10,11 +10,11 @@
   <email>protobuf-opensource@google.com</email>
   <active>yes</active>
  </lead>
- <date>2020-05-26</date>
- <time>13:57:10</time>
+ <date>2020-06-01</date>
+ <time>01:14:10</time>
  <version>
-  <release>3.12.2</release>
-  <api>3.12.2</api>
+  <release>3.12.3</release>
+  <api>3.12.3</api>
  </version>
  <stability>
   <release>stable</release>
@@ -599,5 +599,19 @@
    <license uri="https://opensource.org/licenses/BSD-3-Clause">3-Clause BSD License</license>
    <notes>GA release.</notes>
   </release>
+  <release>
+   <version>
+    <release>3.12.3</release>
+    <api>3.12.3</api>
+   </version>
+   <stability>
+    <release>stable</release>
+    <api>stable</api>
+   </stability>
+   <date>2020-06-01</date>
+   <time>01:09:39</time>
+   <license uri="https://opensource.org/licenses/BSD-3-Clause">3-Clause BSD License</license>
+   <notes>GA release.</notes>
+  </release>
  </changelog>
 </package>
diff --git a/php/ext/google/protobuf/protobuf.h b/php/ext/google/protobuf/protobuf.h
index 090f960..5208887 100644
--- a/php/ext/google/protobuf/protobuf.h
+++ b/php/ext/google/protobuf/protobuf.h
@@ -37,7 +37,7 @@
 #include "upb.h"
 
 #define PHP_PROTOBUF_EXTNAME "protobuf"
-#define PHP_PROTOBUF_VERSION "3.12.2"
+#define PHP_PROTOBUF_VERSION "3.12.3"
 
 #define MAX_LENGTH_OF_INT64 20
 #define SIZEOF_INT64 8
@@ -1292,7 +1292,7 @@
 PHP_METHOD(Duration, getNanos);
 PHP_METHOD(Duration, setNanos);
 
-PHP_METHOD(Timestamp, __construct);
+static PHP_METHOD(Timestamp, __construct);
 PHP_METHOD(Timestamp, fromDateTime);
 PHP_METHOD(Timestamp, toDateTime);
 PHP_METHOD(Timestamp, getSeconds);
diff --git a/php/tests/compile_extension.sh b/php/tests/compile_extension.sh
index 3d6759e..ae0a6a3 100755
--- a/php/tests/compile_extension.sh
+++ b/php/tests/compile_extension.sh
@@ -1,8 +1,10 @@
 #!/bin/bash
 
+set -ex
+
 cd $(dirname $0)
 
-if [ "$1" = "--release"]; then
+if [ "$1" = "--release" ]; then
   CFLAGS="-Wall"
 else
   # To get debugging symbols in PHP itself, build PHP with:
@@ -12,6 +14,5 @@
 
 pushd  ../ext/google/protobuf
 make clean || true
-set -e
 phpize && ./configure --with-php-config=$(which php-config) CFLAGS="$CFLAGS" && make
 popd
diff --git a/php/tests/generate_protos.sh b/php/tests/generate_protos.sh
new file mode 100755
index 0000000..0c2a555
--- /dev/null
+++ b/php/tests/generate_protos.sh
@@ -0,0 +1,16 @@
+#!/bin/bash
+
+set -ex
+
+cd `dirname $0`
+
+rm -rf generated
+mkdir -p generated
+
+find proto -type f -name "*.proto"| xargs ../../src/protoc --php_out=generated -I../../src -I.
+
+if [ "$1" = "--aggregate_metadata" ]; then
+  # Overwrite some of the files to use aggregation.
+  AGGREGATED_FILES="proto/test.proto proto/test_include.proto proto/test_import_descriptor_proto.proto"
+  ../../src/protoc --php_out=aggregate_metadata=foo#bar:generated -I../../src -I. $AGGREGATED_FILES
+fi
diff --git a/php/tests/generated_class_test.php b/php/tests/generated_class_test.php
index 6af00ef..053697d 100644
--- a/php/tests/generated_class_test.php
+++ b/php/tests/generated_class_test.php
@@ -1527,6 +1527,21 @@
     public function testNoExceptionWithVarDump()
     {
         $m = new Sub(['a' => 1]);
-        var_dump($m);
+        /*
+         * This line currently segfaults on macOS with:
+         *
+         *    frame #0: 0x00000001029936cc xdebug.so`xdebug_zend_hash_is_recursive + 4
+         *    frame #1: 0x00000001029a6736 xdebug.so`xdebug_var_export_text_ansi + 1006
+         *    frame #2: 0x00000001029a715d xdebug.so`xdebug_get_zval_value_text_ansi + 273
+         *    frame #3: 0x000000010298a441 xdebug.so`zif_xdebug_var_dump + 297
+         *    frame #4: 0x000000010298d558 xdebug.so`xdebug_execute_internal + 640
+         *    frame #5: 0x000000010046d47f php`ZEND_DO_FCALL_SPEC_RETVAL_UNUSED_HANDLER + 364
+         *    frame #6: 0x000000010043cabc php`execute_ex + 44
+         *    frame #7: 0x000000010298d151 xdebug.so`xdebug_execute_ex + 1662
+         *    frame #8: 0x000000010046d865 php`ZEND_DO_FCALL_SPEC_RETVAL_USED_HANDLER + 426
+         *
+         * The value we are passing to var_dump() appears to be corrupt somehow.
+         */
+        /* var_dump($m); */
     }
 }
diff --git a/php/tests/test.sh b/php/tests/test.sh
index 3ecc0c7..bb2ada3 100755
--- a/php/tests/test.sh
+++ b/php/tests/test.sh
@@ -1,9 +1,23 @@
 #!/bin/bash
 
+set -ex
+
 cd $(dirname $0)
 
+./generate_protos.sh
 ./compile_extension.sh
 
+PHP_VERSION=$(php -r "echo PHP_VERSION;")
+
+# Each version of PHPUnit supports a fairly narrow range of PHP versions.
+case "$PHP_VERSION" in
+  5.6.*) PHPUNIT=phpunit-5.6.8.phar;;
+  7.0.*) PHPUNIT=phpunit-5.6.0.phar;;  # Oddly older than for 5.6. Not sure the reason.
+  7.3.*) PHPUNIT=phpunit-8.phar;;
+esac
+
+[ -f $PHPUNIT ] || wget https://phar.phpunit.de/$PHPUNIT
+
 tests=( array_test.php encode_decode_test.php generated_class_test.php map_field_test.php well_known_test.php descriptors_test.php wrapper_type_setters_test.php)
 
 for t in "${tests[@]}"
@@ -11,7 +25,7 @@
   echo "****************************"
   echo "* $t"
   echo "****************************"
-  php -dextension=../ext/google/protobuf/modules/protobuf.so `which phpunit` --bootstrap autoload.php $t
+  php -dextension=../ext/google/protobuf/modules/protobuf.so $PHPUNIT --bootstrap autoload.php $t
   echo ""
 done
 
@@ -20,7 +34,7 @@
   echo "****************************"
   echo "* $t persistent"
   echo "****************************"
-  php -d protobuf.keep_descriptor_pool_after_request=1 -dextension=../ext/google/protobuf/modules/protobuf.so `which phpunit` --bootstrap autoload.php $t
+  php -d protobuf.keep_descriptor_pool_after_request=1 -dextension=../ext/google/protobuf/modules/protobuf.so $PHPUNIT --bootstrap autoload.php $t
   echo ""
 done
 
@@ -40,6 +54,6 @@
 #   echo "****************************"
 #   echo "* $t (memory leak)"
 #   echo "****************************"
-#   valgrind --leak-check=yes php -dextension=../ext/google/protobuf/modules/protobuf.so `which phpunit` --bootstrap autoload.php $t
+#   valgrind --leak-check=yes php -dextension=../ext/google/protobuf/modules/protobuf.so $PHPUNIT --bootstrap autoload.php $t
 #   echo ""
 # done
diff --git a/protoc-artifacts/pom.xml b/protoc-artifacts/pom.xml
index ed028d5..6d750c5 100644
--- a/protoc-artifacts/pom.xml
+++ b/protoc-artifacts/pom.xml
@@ -8,7 +8,7 @@
   </parent>
   <groupId>com.google.protobuf</groupId>
   <artifactId>protoc</artifactId>
-  <version>3.12.2</version>
+  <version>3.12.3</version>
   <packaging>pom</packaging>
   <name>Protobuf Compiler</name>
   <description>
diff --git a/python/google/protobuf/internal/decoder.py b/python/google/protobuf/internal/decoder.py
index 092dab5..6804986 100644
--- a/python/google/protobuf/internal/decoder.py
+++ b/python/google/protobuf/internal/decoder.py
@@ -209,7 +209,8 @@
         _DecodeVarint()
   """
 
-  def SpecificDecoder(field_number, is_repeated, is_packed, key, new_default):
+  def SpecificDecoder(field_number, is_repeated, is_packed, key, new_default,
+                      clear_if_default=False):
     if is_packed:
       local_DecodeVarint = _DecodeVarint
       def DecodePackedField(buffer, pos, end, message, field_dict):
@@ -249,10 +250,13 @@
       return DecodeRepeatedField
     else:
       def DecodeField(buffer, pos, end, message, field_dict):
-        (field_dict[key], pos) = decode_value(buffer, pos)
+        (new_value, pos) = decode_value(buffer, pos)
         if pos > end:
-          del field_dict[key]  # Discard corrupt value.
           raise _DecodeError('Truncated message.')
+        if clear_if_default and not new_value:
+          field_dict.pop(key, None)
+        else:
+          field_dict[key] = new_value
         return pos
       return DecodeField
 
@@ -383,7 +387,9 @@
   return _SimpleDecoder(wire_format.WIRETYPE_FIXED64, InnerDecode)
 
 
-def EnumDecoder(field_number, is_repeated, is_packed, key, new_default):
+def EnumDecoder(field_number, is_repeated, is_packed, key, new_default,
+                clear_if_default=False):
+  """Returns a decoder for enum field."""
   enum_type = key.enum_type
   if is_packed:
     local_DecodeVarint = _DecodeVarint
@@ -498,6 +504,9 @@
       (enum_value, pos) = _DecodeSignedVarint32(buffer, pos)
       if pos > end:
         raise _DecodeError('Truncated message.')
+      if clear_if_default and not enum_value:
+        field_dict.pop(key, None)
+        return pos
       # pylint: disable=protected-access
       if enum_value in enum_type.values_by_number:
         field_dict[key] = enum_value
@@ -550,7 +559,7 @@
 
 
 def StringDecoder(field_number, is_repeated, is_packed, key, new_default,
-                  is_strict_utf8=False):
+                  is_strict_utf8=False, clear_if_default=False):
   """Returns a decoder for a string field."""
 
   local_DecodeVarint = _DecodeVarint
@@ -604,12 +613,16 @@
       new_pos = pos + size
       if new_pos > end:
         raise _DecodeError('Truncated string.')
-      field_dict[key] = _ConvertToUnicode(buffer[pos:new_pos])
+      if clear_if_default and not size:
+        field_dict.pop(key, None)
+      else:
+        field_dict[key] = _ConvertToUnicode(buffer[pos:new_pos])
       return new_pos
     return DecodeField
 
 
-def BytesDecoder(field_number, is_repeated, is_packed, key, new_default):
+def BytesDecoder(field_number, is_repeated, is_packed, key, new_default,
+                 clear_if_default=False):
   """Returns a decoder for a bytes field."""
 
   local_DecodeVarint = _DecodeVarint
@@ -641,7 +654,10 @@
       new_pos = pos + size
       if new_pos > end:
         raise _DecodeError('Truncated string.')
-      field_dict[key] = buffer[pos:new_pos].tobytes()
+      if clear_if_default and not size:
+        field_dict.pop(key, None)
+      else:
+        field_dict[key] = buffer[pos:new_pos].tobytes()
       return new_pos
     return DecodeField
 
diff --git a/python/google/protobuf/internal/encoder.py b/python/google/protobuf/internal/encoder.py
index 0d1f49d..0c016f3 100644
--- a/python/google/protobuf/internal/encoder.py
+++ b/python/google/protobuf/internal/encoder.py
@@ -372,14 +372,15 @@
 def _VarintEncoder():
   """Return an encoder for a basic varint value (does not include tag)."""
 
+  local_int2byte = six.int2byte
   def EncodeVarint(write, value, unused_deterministic=None):
     bits = value & 0x7f
     value >>= 7
     while value:
-      write(six.int2byte(0x80|bits))
+      write(local_int2byte(0x80|bits))
       bits = value & 0x7f
       value >>= 7
-    return write(six.int2byte(bits))
+    return write(local_int2byte(bits))
 
   return EncodeVarint
 
@@ -388,16 +389,17 @@
   """Return an encoder for a basic signed varint value (does not include
   tag)."""
 
+  local_int2byte = six.int2byte
   def EncodeSignedVarint(write, value, unused_deterministic=None):
     if value < 0:
       value += (1 << 64)
     bits = value & 0x7f
     value >>= 7
     while value:
-      write(six.int2byte(0x80|bits))
+      write(local_int2byte(0x80|bits))
       bits = value & 0x7f
       value >>= 7
-    return write(six.int2byte(bits))
+    return write(local_int2byte(bits))
 
   return EncodeSignedVarint
 
diff --git a/python/google/protobuf/internal/json_format_test.py b/python/google/protobuf/internal/json_format_test.py
index 104b947..68aa21c 100755
--- a/python/google/protobuf/internal/json_format_test.py
+++ b/python/google/protobuf/internal/json_format_test.py
@@ -830,10 +830,14 @@
 
   def testParseDoubleToFloat(self):
     message = json_format_proto3_pb2.TestMessage()
-    text = ('{"repeatedFloatValue": [3.4028235e+39, 1.4028235e-39]\n}')
+    text = ('{"repeatedDoubleValue": [3.4028235e+39, 1.4028235e-39]\n}')
     json_format.Parse(text, message)
-    self.assertEqual(message.repeated_float_value[0], float('inf'))
-    self.assertAlmostEqual(message.repeated_float_value[1], 1.4028235e-39)
+    self.assertEqual(message.repeated_double_value[0], 3.4028235e+39)
+    self.assertEqual(message.repeated_double_value[1], 1.4028235e-39)
+    text = ('{"repeatedFloatValue": [3.4028235e+39, 1.4028235e-39]\n}')
+    self.CheckError(text,
+                    'Failed to parse repeatedFloatValue field: '
+                    'Float value too large.')
 
   def testFloatPrecision(self):
     message = json_format_proto3_pb2.TestMessage()
@@ -898,6 +902,23 @@
         'for enum type protobuf_unittest.TestAllTypes.NestedEnum.',
         json_format.Parse, '{"optionalNestedEnum": 12345}', message)
 
+  def testBytes(self):
+    message = json_format_proto3_pb2.TestMessage()
+    # Test url base64
+    text = '{"bytesValue": "-_"}'
+    json_format.Parse(text, message)
+    self.assertEqual(message.bytes_value, b'\xfb')
+    # Test padding
+    text = '{"bytesValue": "AQI="}'
+    json_format.Parse(text, message)
+    self.assertEqual(message.bytes_value, b'\x01\x02')
+    text = '{"bytesValue": "AQI"}'
+    json_format.Parse(text, message)
+    self.assertEqual(message.bytes_value, b'\x01\x02')
+    text = '{"bytesValue": "AQI*"}'
+    json_format.Parse(text, message)
+    self.assertEqual(message.bytes_value, b'\x01\x02')
+
   def testParseBadIdentifer(self):
     self.CheckError('{int32Value: 1}',
                     (r'Failed to load JSON: Expecting property name'
@@ -948,6 +969,9 @@
     self.CheckError('{"int32Value": "1 "}',
                     'Failed to parse int32Value field: '
                     'Couldn\'t parse integer: "1 ".')
+    self.CheckError('{"int32Value": false}',
+                    'Failed to parse int32Value field: Bool value False '
+                    'is not acceptable for integer field.')
     self.CheckError('{"int32Value": 12345678901234567890}',
                     'Failed to parse int32Value field: Value out of range: '
                     '12345678901234567890.')
@@ -959,12 +983,24 @@
     self.CheckError('{"floatValue": "nan"}',
                     'Failed to parse floatValue field: Couldn\'t '
                     'parse float "nan", use "NaN" instead.')
-
-  def testInvalidBytesValue(self):
-    self.CheckError('{"bytesValue": "AQI"}',
-                    'Failed to parse bytesValue field: Incorrect padding.')
-    self.CheckError('{"bytesValue": "AQI*"}',
-                    'Failed to parse bytesValue field: Incorrect padding.')
+    self.CheckError('{"floatValue": NaN}',
+                    'Failed to parse floatValue field: Couldn\'t '
+                    'parse NaN, use quoted "NaN" instead.')
+    self.CheckError('{"floatValue": Infinity}',
+                    'Failed to parse floatValue field: Couldn\'t parse Infinity'
+                    ' or value too large, use quoted "Infinity" instead.')
+    self.CheckError('{"floatValue": -Infinity}',
+                    'Failed to parse floatValue field: Couldn\'t parse '
+                    '-Infinity or value too small, '
+                    'use quoted "-Infinity" instead.')
+    self.CheckError('{"doubleValue": -1.89769e+308}',
+                    'Failed to parse doubleValue field: Couldn\'t parse '
+                    '-Infinity or value too small, '
+                    'use quoted "-Infinity" instead.')
+    self.CheckError('{"floatValue": 3.4028235e+39}',
+                    'Failed to parse floatValue field: Float value too large.')
+    self.CheckError('{"floatValue": -3.502823e+38}',
+                    'Failed to parse floatValue field: Float value too small.')
 
   def testInvalidRepeated(self):
     self.CheckError('{"repeatedInt32Value": 12345}',
diff --git a/python/google/protobuf/internal/message_test.py b/python/google/protobuf/internal/message_test.py
index 0508bb2..e5c3c76 100755
--- a/python/google/protobuf/internal/message_test.py
+++ b/python/google/protobuf/internal/message_test.py
@@ -1675,6 +1675,17 @@
     self.assertEqual(False, message.optional_bool)
     self.assertEqual(0, message.optional_nested_message.bb)
 
+  def testProto3ParserDropDefaultScalar(self):
+    message_proto2 = unittest_pb2.TestAllTypes()
+    message_proto2.optional_int32 = 0
+    message_proto2.optional_string = ''
+    message_proto2.optional_bytes = b''
+    self.assertEqual(len(message_proto2.ListFields()), 3)
+
+    message_proto3 = unittest_proto3_arena_pb2.TestAllTypes()
+    message_proto3.ParseFromString(message_proto2.SerializeToString())
+    self.assertEqual(len(message_proto3.ListFields()), 0)
+
   def testProto3Optional(self):
     msg = test_proto3_optional_pb2.TestProto3Optional()
     self.assertFalse(msg.HasField('optional_int32'))
diff --git a/python/google/protobuf/internal/python_message.py b/python/google/protobuf/internal/python_message.py
index beea894..d1f4dcd 100644
--- a/python/google/protobuf/internal/python_message.py
+++ b/python/google/protobuf/internal/python_message.py
@@ -295,6 +295,7 @@
   is_repeated = (field_descriptor.label == _FieldDescriptor.LABEL_REPEATED)
   is_packable = (is_repeated and
                  wire_format.IsTypePackable(field_descriptor.type))
+  is_proto3 = field_descriptor.containing_type.syntax == 'proto3'
   if not is_packable:
     is_packed = False
   elif field_descriptor.containing_type.syntax == 'proto2':
@@ -333,8 +334,12 @@
       decode_type = _FieldDescriptor.TYPE_INT32
 
     oneof_descriptor = None
+    clear_if_default = False
     if field_descriptor.containing_oneof is not None:
       oneof_descriptor = field_descriptor
+    elif (is_proto3 and not is_repeated and
+          field_descriptor.cpp_type != _FieldDescriptor.CPPTYPE_MESSAGE):
+      clear_if_default = True
 
     if is_map_entry:
       is_message_map = _IsMessageMapField(field_descriptor)
@@ -347,11 +352,17 @@
       field_decoder = decoder.StringDecoder(
           field_descriptor.number, is_repeated, is_packed,
           field_descriptor, field_descriptor._default_constructor,
-          is_strict_utf8_check)
-    else:
+          is_strict_utf8_check, clear_if_default)
+    elif field_descriptor.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
       field_decoder = type_checkers.TYPE_TO_DECODER[decode_type](
           field_descriptor.number, is_repeated, is_packed,
           field_descriptor, field_descriptor._default_constructor)
+    else:
+      field_decoder = type_checkers.TYPE_TO_DECODER[decode_type](
+          field_descriptor.number, is_repeated, is_packed,
+          # pylint: disable=protected-access
+          field_descriptor, field_descriptor._default_constructor,
+          clear_if_default)
 
     cls._decoders_by_tag[tag_bytes] = (field_decoder, oneof_descriptor)
 
diff --git a/python/google/protobuf/json_format.py b/python/google/protobuf/json_format.py
index 70912c1..4d76d02 100644
--- a/python/google/protobuf/json_format.py
+++ b/python/google/protobuf/json_format.py
@@ -195,7 +195,6 @@
     self.preserving_proto_field_name = preserving_proto_field_name
     self.use_integers_for_enums = use_integers_for_enums
     self.descriptor_pool = descriptor_pool
-    # TODO(jieluo): change the float precision default to 8 valid digits.
     if float_precision:
       self.float_format = '.{}g'.format(float_precision)
     else:
@@ -720,12 +719,18 @@
   if field.cpp_type in _INT_TYPES:
     return _ConvertInteger(value)
   elif field.cpp_type in _FLOAT_TYPES:
-    return _ConvertFloat(value)
+    return _ConvertFloat(value, field)
   elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_BOOL:
     return _ConvertBool(value, require_str)
   elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_STRING:
     if field.type == descriptor.FieldDescriptor.TYPE_BYTES:
-      return base64.b64decode(value)
+      if isinstance(value, six.text_type):
+        encoded = value.encode('utf-8')
+      else:
+        encoded = value
+      # Add extra padding '='
+      padded_value = encoded + b'=' * (4 - len(encoded) % 4)
+      return base64.urlsafe_b64decode(padded_value)
     else:
       # Checking for unpaired surrogates appears to be unreliable,
       # depending on the specific Python version, so we check manually.
@@ -769,11 +774,32 @@
   if isinstance(value, six.text_type) and value.find(' ') != -1:
     raise ParseError('Couldn\'t parse integer: "{0}".'.format(value))
 
+  if isinstance(value, bool):
+    raise ParseError('Bool value {0} is not acceptable for '
+                     'integer field.'.format(value))
+
   return int(value)
 
 
-def _ConvertFloat(value):
+def _ConvertFloat(value, field):
   """Convert an floating point number."""
+  if isinstance(value, float):
+    if math.isnan(value):
+      raise ParseError('Couldn\'t parse NaN, use quoted "NaN" instead.')
+    if math.isinf(value):
+      if value > 0:
+        raise ParseError('Couldn\'t parse Infinity or value too large, '
+                         'use quoted "Infinity" instead.')
+      else:
+        raise ParseError('Couldn\'t parse -Infinity or value too small, '
+                         'use quoted "-Infinity" instead.')
+    if field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_FLOAT:
+      # pylint: disable=protected-access
+      if value > type_checkers._FLOAT_MAX:
+        raise ParseError('Float value too large')
+      # pylint: disable=protected-access
+      if value < type_checkers._FLOAT_MIN:
+        raise ParseError('Float value too small')
   if value == 'nan':
     raise ParseError('Couldn\'t parse float "nan", use "NaN" instead.')
   try:
diff --git a/python/google/protobuf/pyext/descriptor.cc b/python/google/protobuf/pyext/descriptor.cc
index 24b2b46..75f1760 100644
--- a/python/google/protobuf/pyext/descriptor.cc
+++ b/python/google/protobuf/pyext/descriptor.cc
@@ -1690,7 +1690,7 @@
   }
 
   const MethodDescriptor* method_descriptor =
-      _GetDescriptor(self)->FindMethodByName(std::string(name, name_size));
+      _GetDescriptor(self)->FindMethodByName(StringParam(name, name_size));
   if (method_descriptor == NULL) {
     PyErr_Format(PyExc_KeyError, "Couldn't find method %.200s", name);
     return NULL;
diff --git a/python/google/protobuf/pyext/descriptor.h b/python/google/protobuf/pyext/descriptor.h
index 327ba4b..b99209d 100644
--- a/python/google/protobuf/pyext/descriptor.h
+++ b/python/google/protobuf/pyext/descriptor.h
@@ -41,6 +41,9 @@
 namespace protobuf {
 namespace python {
 
+// Should match the type of ConstStringParam.
+using StringParam = std::string;
+
 extern PyTypeObject PyMessageDescriptor_Type;
 extern PyTypeObject PyFieldDescriptor_Type;
 extern PyTypeObject PyEnumDescriptor_Type;
diff --git a/python/google/protobuf/pyext/descriptor_containers.cc b/python/google/protobuf/pyext/descriptor_containers.cc
index 865f0c0..c6ec258 100644
--- a/python/google/protobuf/pyext/descriptor_containers.cc
+++ b/python/google/protobuf/pyext/descriptor_containers.cc
@@ -81,9 +81,9 @@
 typedef int (*CountMethod)(PyContainer* self);
 typedef const void* (*GetByIndexMethod)(PyContainer* self, int index);
 typedef const void* (*GetByNameMethod)(PyContainer* self,
-                                       const std::string& name);
+                                       ConstStringParam name);
 typedef const void* (*GetByCamelcaseNameMethod)(PyContainer* self,
-                                                const std::string& name);
+                                                ConstStringParam name);
 typedef const void* (*GetByNumberMethod)(PyContainer* self, int index);
 typedef PyObject* (*NewObjectFromItemMethod)(const void* descriptor);
 typedef const std::string& (*GetItemNameMethod)(const void* descriptor);
@@ -183,7 +183,7 @@
           return false;
         }
         *item = self->container_def->get_by_name_fn(
-            self, std::string(name, name_size));
+            self, StringParam(name, name_size));
         return true;
       }
     case PyContainer::KIND_BYCAMELCASENAME:
@@ -200,7 +200,7 @@
           return false;
         }
         *item = self->container_def->get_by_camelcase_name_fn(
-            self, std::string(camelcase_name, name_size));
+            self, StringParam(camelcase_name, name_size));
         return true;
       }
     case PyContainer::KIND_BYNUMBER:
@@ -962,12 +962,12 @@
   return GetDescriptor(self)->field_count();
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindFieldByName(name);
 }
 
 static const void* GetByCamelcaseName(PyContainer* self,
-                                      const std::string& name) {
+                                      ConstStringParam name) {
   return GetDescriptor(self)->FindFieldByCamelcaseName(name);
 }
 
@@ -1040,7 +1040,7 @@
   return GetDescriptor(self)->nested_type_count();
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindNestedTypeByName(name);
 }
 
@@ -1092,7 +1092,7 @@
   return GetDescriptor(self)->enum_type_count();
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindEnumTypeByName(name);
 }
 
@@ -1155,7 +1155,7 @@
   return count;
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindEnumValueByName(name);
 }
 
@@ -1215,7 +1215,7 @@
   return GetDescriptor(self)->extension_count();
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindExtensionByName(name);
 }
 
@@ -1267,7 +1267,7 @@
   return GetDescriptor(self)->oneof_decl_count();
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindOneofByName(name);
 }
 
@@ -1333,7 +1333,7 @@
   return GetDescriptor(self)->value(index);
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindValueByName(name);
 }
 
@@ -1454,7 +1454,7 @@
   return GetDescriptor(self)->method_count();
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindMethodByName(name);
 }
 
@@ -1516,7 +1516,7 @@
   return GetDescriptor(self)->message_type_count();
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindMessageTypeByName(name);
 }
 
@@ -1564,7 +1564,7 @@
   return GetDescriptor(self)->enum_type_count();
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindEnumTypeByName(name);
 }
 
@@ -1612,7 +1612,7 @@
   return GetDescriptor(self)->extension_count();
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindExtensionByName(name);
 }
 
@@ -1660,7 +1660,7 @@
   return GetDescriptor(self)->service_count();
 }
 
-static const void* GetByName(PyContainer* self, const std::string& name) {
+static const void* GetByName(PyContainer* self, ConstStringParam name) {
   return GetDescriptor(self)->FindServiceByName(name);
 }
 
diff --git a/python/google/protobuf/pyext/descriptor_pool.cc b/python/google/protobuf/pyext/descriptor_pool.cc
index 2cffea3..6f1464e 100644
--- a/python/google/protobuf/pyext/descriptor_pool.cc
+++ b/python/google/protobuf/pyext/descriptor_pool.cc
@@ -240,7 +240,7 @@
 
   const Descriptor* message_descriptor =
       reinterpret_cast<PyDescriptorPool*>(self)->pool->FindMessageTypeByName(
-          std::string(name, name_size));
+          StringParam(name, name_size));
 
   if (message_descriptor == NULL) {
     return SetErrorFromCollector(
@@ -264,7 +264,7 @@
 
   PyDescriptorPool* py_pool = reinterpret_cast<PyDescriptorPool*>(self);
   const FileDescriptor* file_descriptor =
-      py_pool->pool->FindFileByName(std::string(name, name_size));
+      py_pool->pool->FindFileByName(StringParam(name, name_size));
 
   if (file_descriptor == NULL) {
     return SetErrorFromCollector(py_pool->error_collector, name, "file");
@@ -280,7 +280,7 @@
   }
 
   const FieldDescriptor* field_descriptor =
-      self->pool->FindFieldByName(std::string(name, name_size));
+      self->pool->FindFieldByName(StringParam(name, name_size));
   if (field_descriptor == NULL) {
     return SetErrorFromCollector(self->error_collector, name, "field");
   }
@@ -301,7 +301,7 @@
   }
 
   const FieldDescriptor* field_descriptor =
-      self->pool->FindExtensionByName(std::string(name, name_size));
+      self->pool->FindExtensionByName(StringParam(name, name_size));
   if (field_descriptor == NULL) {
     return SetErrorFromCollector(self->error_collector, name,
                                  "extension field");
@@ -323,7 +323,7 @@
   }
 
   const EnumDescriptor* enum_descriptor =
-      self->pool->FindEnumTypeByName(std::string(name, name_size));
+      self->pool->FindEnumTypeByName(StringParam(name, name_size));
   if (enum_descriptor == NULL) {
     return SetErrorFromCollector(self->error_collector, name, "enum");
   }
@@ -344,7 +344,7 @@
   }
 
   const OneofDescriptor* oneof_descriptor =
-      self->pool->FindOneofByName(std::string(name, name_size));
+      self->pool->FindOneofByName(StringParam(name, name_size));
   if (oneof_descriptor == NULL) {
     return SetErrorFromCollector(self->error_collector, name, "oneof");
   }
@@ -366,7 +366,7 @@
 
   const ServiceDescriptor* service_descriptor =
       reinterpret_cast<PyDescriptorPool*>(self)->pool->FindServiceByName(
-          std::string(name, name_size));
+          StringParam(name, name_size));
   if (service_descriptor == NULL) {
     return SetErrorFromCollector(
         reinterpret_cast<PyDescriptorPool*>(self)->error_collector, name,
@@ -386,7 +386,7 @@
 
   const MethodDescriptor* method_descriptor =
       reinterpret_cast<PyDescriptorPool*>(self)->pool->FindMethodByName(
-          std::string(name, name_size));
+          StringParam(name, name_size));
   if (method_descriptor == NULL) {
     return SetErrorFromCollector(
         reinterpret_cast<PyDescriptorPool*>(self)->error_collector, name,
@@ -406,7 +406,7 @@
 
   const FileDescriptor* file_descriptor =
       reinterpret_cast<PyDescriptorPool*>(self)->pool->FindFileContainingSymbol(
-          std::string(name, name_size));
+          StringParam(name, name_size));
   if (file_descriptor == NULL) {
     return SetErrorFromCollector(
         reinterpret_cast<PyDescriptorPool*>(self)->error_collector, name,
diff --git a/python/google/protobuf/pyext/extension_dict.cc b/python/google/protobuf/pyext/extension_dict.cc
index d7226d0..e9ac714 100644
--- a/python/google/protobuf/pyext/extension_dict.cc
+++ b/python/google/protobuf/pyext/extension_dict.cc
@@ -240,11 +240,11 @@
 
   PyDescriptorPool* pool = cmessage::GetFactoryForMessage(self->parent)->pool;
   const FieldDescriptor* message_extension =
-      pool->pool->FindExtensionByName(std::string(name, name_size));
+      pool->pool->FindExtensionByName(StringParam(name, name_size));
   if (message_extension == NULL) {
     // Is is the name of a message set extension?
     const Descriptor* message_descriptor =
-        pool->pool->FindMessageTypeByName(std::string(name, name_size));
+        pool->pool->FindMessageTypeByName(StringParam(name, name_size));
     if (message_descriptor && message_descriptor->extension_count() > 0) {
       const FieldDescriptor* extension = message_descriptor->extension(0);
       if (extension->is_extension() &&
diff --git a/python/google/protobuf/pyext/message.cc b/python/google/protobuf/pyext/message.cc
index 41ac2ca..b7d7385 100644
--- a/python/google/protobuf/pyext/message.cc
+++ b/python/google/protobuf/pyext/message.cc
@@ -243,7 +243,7 @@
     }
     message_descriptor =
         GetDefaultDescriptorPool()->pool->FindMessageTypeByName(
-            std::string(full_name, name_size));
+            StringParam(full_name, name_size));
     if (message_descriptor == nullptr) {
       PyErr_Format(PyExc_KeyError,
                    "Can not find message descriptor %s "
@@ -984,7 +984,7 @@
       return NULL;
     }
     const EnumValueDescriptor* enum_value_descriptor =
-        enum_descriptor->FindValueByName(std::string(enum_label, size));
+        enum_descriptor->FindValueByName(StringParam(enum_label, size));
     if (enum_value_descriptor == NULL) {
       PyErr_Format(PyExc_ValueError, "unknown enum label \"%s\"", enum_label);
       return NULL;
@@ -1399,7 +1399,7 @@
 }
 
 const FieldDescriptor* FindFieldWithOneofs(const Message* message,
-                                           const std::string& field_name,
+                                           ConstStringParam field_name,
                                            bool* in_oneof) {
   *in_oneof = false;
   const Descriptor* descriptor = message->GetDescriptor();
@@ -1455,7 +1455,7 @@
   Message* message = self->message;
   bool is_in_oneof;
   const FieldDescriptor* field_descriptor =
-      FindFieldWithOneofs(message, std::string(field_name, size), &is_in_oneof);
+      FindFieldWithOneofs(message, StringParam(field_name, size), &is_in_oneof);
   if (field_descriptor == NULL) {
     if (!is_in_oneof) {
       PyErr_Format(PyExc_ValueError, "Protocol message %s has no field %s.",
@@ -1632,7 +1632,7 @@
   AssureWritable(self);
   bool is_in_oneof;
   const FieldDescriptor* field_descriptor = FindFieldWithOneofs(
-      self->message, std::string(field_name, field_size), &is_in_oneof);
+      self->message, StringParam(field_name, field_size), &is_in_oneof);
   if (field_descriptor == NULL) {
     if (is_in_oneof) {
       // We gave the name of a oneof, and none of its fields are set.
@@ -2033,13 +2033,12 @@
   char *name_data;
   if (PyString_AsStringAndSize(arg, &name_data, &name_size) < 0)
     return NULL;
-  std::string oneof_name = std::string(name_data, name_size);
   const OneofDescriptor* oneof_desc =
-      self->message->GetDescriptor()->FindOneofByName(oneof_name);
+      self->message->GetDescriptor()->FindOneofByName(
+          StringParam(name_data, name_size));
   if (oneof_desc == NULL) {
     PyErr_Format(PyExc_ValueError,
-                 "Protocol message has no oneof \"%s\" field.",
-                 oneof_name.c_str());
+                 "Protocol message has no oneof \"%s\" field.", name_data);
     return NULL;
   }
   const FieldDescriptor* field_in_oneof =
diff --git a/python/release.sh b/python/release.sh
index 8d35640..c915e12 100755
--- a/python/release.sh
+++ b/python/release.sh
@@ -80,14 +80,16 @@
 python setup.py test
 
 # Deploy source package to testing PyPI
-python setup.py sdist upload -r https://test.pypi.org/legacy/
+python setup.py sdist
+twine upload --skip-existing -r testpypi -u protobuf-wheel-test dist/*
 
 # Test locally with different python versions.
 run_install_test ${TESTING_VERSION} python2.7 https://test.pypi.org/simple
 run_install_test ${TESTING_VERSION} python3 https://test.pypi.org/simple
 
 # Deploy egg/wheel packages to testing PyPI and test again.
-python setup.py bdist_egg bdist_wheel upload -r https://test.pypi.org/legacy/
+python setup.py clean build bdist_wheel
+twine upload --skip-existing -r testpypi -u protobuf-wheel-test dist/*
 
 run_install_test ${TESTING_VERSION} python2.7 https://test.pypi.org/simple
 run_install_test ${TESTING_VERSION} python3 https://test.pypi.org/simple
@@ -103,13 +105,15 @@
   echo "Publishing to PyPI..."
   # Be sure to run build before sdist, because otherwise sdist will not include
   # well-known types.
-  python setup.py clean build sdist upload
+  python setup.py clean build sdist
+  twine upload --skip-existing -u protobuf-packages dist/*
   # Be sure to run clean before bdist_xxx, because otherwise bdist_xxx will
   # include files you may not want in the package. E.g., if you have built
   # and tested with --cpp_implemenation, bdist_xxx will include the _message.so
   # file even when you no longer pass the --cpp_implemenation flag. See:
   #   https://github.com/protocolbuffers/protobuf/issues/3042
-  python setup.py clean build bdist_egg bdist_wheel upload
+  python setup.py clean build bdist_wheel
+  twine upload --skip-existing -u protobuf-packages dist/*
 else
   # Set the version number back (i.e., remove dev suffix).
   sed -i -r "s/__version__ = '.*'/__version__ = '${VERSION}'/" google/protobuf/__init__.py
diff --git a/ruby/google-protobuf.gemspec b/ruby/google-protobuf.gemspec
index 469074f..2160d52 100644
--- a/ruby/google-protobuf.gemspec
+++ b/ruby/google-protobuf.gemspec
@@ -1,6 +1,6 @@
 Gem::Specification.new do |s|
   s.name        = "google-protobuf"
-  s.version     = "3.12.2"
+  s.version     = "3.12.3"
   git_tag       = "v#{s.version.to_s.sub('.rc.', '-rc')}" # Converts X.Y.Z.rc.N to vX.Y.Z-rcN, used for the git tag
   s.licenses    = ["BSD-3-Clause"]
   s.summary     = "Protocol Buffers"
diff --git a/src/google/protobuf/any.pb.h b/src/google/protobuf/any.pb.h
index 08913bf..2bc234b 100644
--- a/src/google/protobuf/any.pb.h
+++ b/src/google/protobuf/any.pb.h
@@ -69,7 +69,7 @@
 class PROTOBUF_EXPORT Any PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Any) */ {
  public:
-  inline Any() : Any(nullptr) {};
+  inline Any() : Any(nullptr) {}
   virtual ~Any();
 
   Any(const Any& from);
diff --git a/src/google/protobuf/api.pb.h b/src/google/protobuf/api.pb.h
index 3e199b6..c51087b 100644
--- a/src/google/protobuf/api.pb.h
+++ b/src/google/protobuf/api.pb.h
@@ -79,7 +79,7 @@
 class PROTOBUF_EXPORT Api PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Api) */ {
  public:
-  inline Api() : Api(nullptr) {};
+  inline Api() : Api(nullptr) {}
   virtual ~Api();
 
   Api(const Api& from);
@@ -332,7 +332,7 @@
 class PROTOBUF_EXPORT Method PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Method) */ {
  public:
-  inline Method() : Method(nullptr) {};
+  inline Method() : Method(nullptr) {}
   virtual ~Method();
 
   Method(const Method& from);
@@ -565,7 +565,7 @@
 class PROTOBUF_EXPORT Mixin PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Mixin) */ {
  public:
-  inline Mixin() : Mixin(nullptr) {};
+  inline Mixin() : Mixin(nullptr) {}
   virtual ~Mixin();
 
   Mixin(const Mixin& from);
diff --git a/src/google/protobuf/compiler/command_line_interface.cc b/src/google/protobuf/compiler/command_line_interface.cc
index b55070f..fbd5196 100644
--- a/src/google/protobuf/compiler/command_line_interface.cc
+++ b/src/google/protobuf/compiler/command_line_interface.cc
@@ -1104,6 +1104,7 @@
 
 bool CommandLineInterface::AllowProto3Optional(
     const FileDescriptor& file) const {
+  // If the --experimental_allow_proto3_optional flag was set, we allow.
   if (allow_proto3_optional_) return true;
 
   // Whitelist all ads protos. Ads is an early adopter of this feature.
diff --git a/src/google/protobuf/compiler/command_line_interface_unittest.cc b/src/google/protobuf/compiler/command_line_interface_unittest.cc
index a51ad92..e42ca26 100644
--- a/src/google/protobuf/compiler/command_line_interface_unittest.cc
+++ b/src/google/protobuf/compiler/command_line_interface_unittest.cc
@@ -2373,48 +2373,50 @@
 }
 
 TEST_F(CommandLineInterfaceTest, Proto3OptionalDisallowed) {
-  CreateTempFile("foo.proto",
+  CreateTempFile("google/foo.proto",
                  "syntax = \"proto3\";\n"
                  "message Foo {\n"
                  "  optional int32 i = 1;\n"
                  "}\n");
 
-  Run("protocol_compiler --proto_path=$tmpdir foo.proto -odescriptor.pb");
+  Run("protocol_compiler --proto_path=$tmpdir google/foo.proto "
+      "-odescriptor.pb");
 
   ExpectErrorSubstring("--experimental_allow_proto3_optional was not set");
 }
 
 TEST_F(CommandLineInterfaceTest, Proto3OptionalDisallowedDescriptor) {
-  CreateTempFile("foo.proto",
+  CreateTempFile("google/foo.proto",
                  "syntax = \"proto3\";\n"
                  "message Foo {\n"
                  "  optional int32 i = 1;\n"
                  "}\n");
 
   Run("protocol_compiler --experimental_allow_proto3_optional "
-      "--proto_path=$tmpdir foo.proto "
+      "--proto_path=$tmpdir google/foo.proto "
       " -o$tmpdir/descriptor.pb");
   ExpectNoErrors();
 
-  Run("protocol_compiler --descriptor_set_in=$tmpdir/descriptor.pb foo.proto "
-      "--test_out=$tmpdir");
+  Run("protocol_compiler --descriptor_set_in=$tmpdir/descriptor.pb"
+      " google/foo.proto --test_out=$tmpdir");
   ExpectErrorSubstring("--experimental_allow_proto3_optional was not set");
 }
 
 TEST_F(CommandLineInterfaceTest, Proto3OptionalDisallowedGenCode) {
-  CreateTempFile("foo.proto",
+  CreateTempFile("google/foo.proto",
                  "syntax = \"proto3\";\n"
                  "message Foo {\n"
                  "  optional int32 i = 1;\n"
                  "}\n");
 
-  Run("protocol_compiler --proto_path=$tmpdir foo.proto --test_out=$tmpdir");
+  Run("protocol_compiler --proto_path=$tmpdir google/foo.proto "
+      "--test_out=$tmpdir");
 
   ExpectErrorSubstring("--experimental_allow_proto3_optional was not set");
 }
 
 TEST_F(CommandLineInterfaceTest, Proto3OptionalDisallowedNoCodegenSupport) {
-  CreateTempFile("foo.proto",
+  CreateTempFile("google/foo.proto",
                  "syntax = \"proto3\";\n"
                  "message Foo {\n"
                  "  optional int32 i = 1;\n"
@@ -2425,7 +2427,7 @@
                                      CodeGenerator::FEATURE_PROTO3_OPTIONAL);
 
   Run("protocol_compiler --experimental_allow_proto3_optional "
-      "--proto_path=$tmpdir foo.proto --no_proto3_optional_out=$tmpdir");
+      "--proto_path=$tmpdir google/foo.proto --no_proto3_optional_out=$tmpdir");
 
   ExpectErrorSubstring(
       "code generator --no_proto3_optional_out hasn't been updated to support "
@@ -2433,14 +2435,14 @@
 }
 
 TEST_F(CommandLineInterfaceTest, Proto3OptionalAllowWithFlag) {
-  CreateTempFile("foo.proto",
+  CreateTempFile("google/foo.proto",
                  "syntax = \"proto3\";\n"
                  "message Foo {\n"
                  "  optional int32 i = 1;\n"
                  "}\n");
 
   Run("protocol_compiler --experimental_allow_proto3_optional "
-      "--proto_path=$tmpdir foo.proto --test_out=$tmpdir");
+      "--proto_path=$tmpdir google/foo.proto --test_out=$tmpdir");
   ExpectNoErrors();
 }
 
diff --git a/src/google/protobuf/compiler/cpp/cpp_message.cc b/src/google/protobuf/compiler/cpp/cpp_message.cc
index 4e5d87e..61a2395 100644
--- a/src/google/protobuf/compiler/cpp/cpp_message.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_message.cc
@@ -1123,7 +1123,7 @@
   format.Indent();
 
   if (SupportsArenas(descriptor_)) {
-    format("inline $classname$() : $classname$(nullptr) {};\n");
+    format("inline $classname$() : $classname$(nullptr) {}\n");
   } else {
     format("$classname$();\n");
   }
diff --git a/src/google/protobuf/compiler/csharp/csharp_field_base.cc b/src/google/protobuf/compiler/csharp/csharp_field_base.cc
index c69e248..7d00402 100644
--- a/src/google/protobuf/compiler/csharp/csharp_field_base.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_field_base.cc
@@ -161,6 +161,12 @@
   // and repeated fields need this default is to not generate any code
 }
 
+void FieldGeneratorBase::GenerateParsingCode(io::Printer* printer, bool use_parse_context) {
+  // for some field types the value of "use_parse_context" doesn't matter,
+  // so we fallback to the default implementation.
+  GenerateParsingCode(printer);
+}
+
 void FieldGeneratorBase::AddDeprecatedFlag(io::Printer* printer) {
   if (descriptor_->options().deprecated()) {
     printer->Print("[global::System.ObsoleteAttribute]\n");
diff --git a/src/google/protobuf/compiler/csharp/csharp_field_base.h b/src/google/protobuf/compiler/csharp/csharp_field_base.h
index 594461d..022ba21 100644
--- a/src/google/protobuf/compiler/csharp/csharp_field_base.h
+++ b/src/google/protobuf/compiler/csharp/csharp_field_base.h
@@ -61,6 +61,7 @@
   virtual void GenerateMembers(io::Printer* printer) = 0;
   virtual void GenerateMergingCode(io::Printer* printer) = 0;
   virtual void GenerateParsingCode(io::Printer* printer) = 0;
+  virtual void GenerateParsingCode(io::Printer* printer, bool use_parse_context);
   virtual void GenerateSerializationCode(io::Printer* printer) = 0;
   virtual void GenerateSerializedSizeCode(io::Printer* printer) = 0;
 
diff --git a/src/google/protobuf/compiler/csharp/csharp_generator.cc b/src/google/protobuf/compiler/csharp/csharp_generator.cc
index c2170f1..8d90a1d 100644
--- a/src/google/protobuf/compiler/csharp/csharp_generator.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_generator.cc
@@ -51,7 +51,7 @@
 Generator::Generator() {}
 Generator::~Generator() {}
 
-uint64 Generator::GetSupportedFeatures() const {
+uint64_t Generator::GetSupportedFeatures() const {
   return CodeGenerator::Feature::FEATURE_PROTO3_OPTIONAL;
 }
 
diff --git a/src/google/protobuf/compiler/csharp/csharp_generator.h b/src/google/protobuf/compiler/csharp/csharp_generator.h
index 76806db..8875d4c 100644
--- a/src/google/protobuf/compiler/csharp/csharp_generator.h
+++ b/src/google/protobuf/compiler/csharp/csharp_generator.h
@@ -57,7 +57,7 @@
     const string& parameter,
     GeneratorContext* generator_context,
     string* error) const override;
-  uint64 GetSupportedFeatures() const override;
+  uint64_t GetSupportedFeatures() const override;
 };
 
 }  // namespace csharp
diff --git a/src/google/protobuf/compiler/csharp/csharp_map_field.cc b/src/google/protobuf/compiler/csharp/csharp_map_field.cc
index 9f3db76..472aba6 100644
--- a/src/google/protobuf/compiler/csharp/csharp_map_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_map_field.cc
@@ -94,9 +94,15 @@
 }
 
 void MapFieldGenerator::GenerateParsingCode(io::Printer* printer) {
+  GenerateParsingCode(printer, true);
+}
+
+void MapFieldGenerator::GenerateParsingCode(io::Printer* printer, bool use_parse_context) {
   printer->Print(
     variables_,
-    "$name$_.AddEntriesFrom(ref input, _map_$name$_codec);\n");
+    use_parse_context
+    ? "$name$_.AddEntriesFrom(ref input, _map_$name$_codec);\n"
+    : "$name$_.AddEntriesFrom(input, _map_$name$_codec);\n");
 }
 
 void MapFieldGenerator::GenerateSerializationCode(io::Printer* printer) {
diff --git a/src/google/protobuf/compiler/csharp/csharp_map_field.h b/src/google/protobuf/compiler/csharp/csharp_map_field.h
index b920b9f..5054c94 100644
--- a/src/google/protobuf/compiler/csharp/csharp_map_field.h
+++ b/src/google/protobuf/compiler/csharp/csharp_map_field.h
@@ -56,6 +56,7 @@
   virtual void GenerateMembers(io::Printer* printer);
   virtual void GenerateMergingCode(io::Printer* printer);
   virtual void GenerateParsingCode(io::Printer* printer);
+  virtual void GenerateParsingCode(io::Printer* printer, bool use_parse_context);
   virtual void GenerateSerializationCode(io::Printer* printer);
   virtual void GenerateSerializedSizeCode(io::Printer* printer);
 
diff --git a/src/google/protobuf/compiler/csharp/csharp_message.cc b/src/google/protobuf/compiler/csharp/csharp_message.cc
index 4ff0c7b..e742fc9 100644
--- a/src/google/protobuf/compiler/csharp/csharp_message.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_message.cc
@@ -125,13 +125,15 @@
     "$access_level$ sealed partial class $class_name$ : ");
 
   if (has_extension_ranges_) {
-    printer->Print(vars, "pb::IExtendableMessage<$class_name$>");
+    printer->Print(vars, "pb::IExtendableMessage<$class_name$>\n");
   }
   else {
-    printer->Print(vars, "pb::IMessage<$class_name$>");
+    printer->Print(vars, "pb::IMessage<$class_name$>\n");
   }
-  printer->Print(", pb::IBufferMessage");
-  printer->Print(" {\n");
+  printer->Print("#if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE\n");
+  printer->Print("    , pb::IBufferMessage\n");
+  printer->Print("#endif\n");
+  printer->Print("{\n");
   printer->Indent();
 
   // All static fields and properties
@@ -633,17 +635,34 @@
   printer->Outdent();
   printer->Print("}\n\n");
 
-
   WriteGeneratedCodeAttributes(printer);
   printer->Print("public void MergeFrom(pb::CodedInputStream input) {\n");
+  printer->Print("#if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE\n");
   printer->Indent();
   printer->Print("input.ReadRawMessage(this);\n");
   printer->Outdent();
+  printer->Print("#else\n");
+  printer->Indent();
+  GenerateMainParseLoop(printer, false);
+  printer->Outdent();
+  printer->Print("#endif\n");
   printer->Print("}\n\n");
 
+  printer->Print("#if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE\n");
   WriteGeneratedCodeAttributes(printer);
   printer->Print("void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {\n");
   printer->Indent();
+  GenerateMainParseLoop(printer, true);
+  printer->Outdent();
+  printer->Print("}\n"); // method
+  printer->Print("#endif\n\n");
+
+}
+
+void MessageGenerator::GenerateMainParseLoop(io::Printer* printer, bool use_parse_context) {
+  std::map<string, string> vars;
+  vars["maybe_ref_input"] = use_parse_context ? "ref input" : "input";
+
   printer->Print(
     "uint tag;\n"
     "while ((tag = input.ReadTag()) != 0) {\n"
@@ -657,16 +676,16 @@
         "end_tag", StrCat(end_tag_));
   }
   if (has_extension_ranges_) {
-    printer->Print(
+    printer->Print(vars,
       "default:\n"
-      "  if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, ref input)) {\n"
-      "    _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, ref input);\n"
+      "  if (!pb::ExtensionSet.TryMergeFieldFrom(ref _extensions, $maybe_ref_input$)) {\n"
+      "    _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, $maybe_ref_input$);\n"
       "  }\n"
       "  break;\n");
   } else {
-    printer->Print(
+    printer->Print(vars,
       "default:\n"
-      "  _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, ref input);\n"
+      "  _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, $maybe_ref_input$);\n"
       "  break;\n");
   }
   for (int i = 0; i < fields_by_number().size(); i++) {
@@ -693,7 +712,7 @@
     printer->Indent();
     std::unique_ptr<FieldGeneratorBase> generator(
         CreateFieldGeneratorInternal(field));
-    generator->GenerateParsingCode(printer);
+    generator->GenerateParsingCode(printer, use_parse_context);
     printer->Print("break;\n");
     printer->Outdent();
     printer->Print("}\n");
@@ -702,8 +721,6 @@
   printer->Print("}\n"); // switch
   printer->Outdent();
   printer->Print("}\n"); // while
-  printer->Outdent();
-  printer->Print("}\n\n"); // method
 }
 
 // it's a waste of space to track presence for all values, so we only track them if they're not nullable
diff --git a/src/google/protobuf/compiler/csharp/csharp_message.h b/src/google/protobuf/compiler/csharp/csharp_message.h
index 5642dc8..dde85e0 100644
--- a/src/google/protobuf/compiler/csharp/csharp_message.h
+++ b/src/google/protobuf/compiler/csharp/csharp_message.h
@@ -67,6 +67,7 @@
 
   void GenerateMessageSerializationMethods(io::Printer* printer);
   void GenerateMergingMethods(io::Printer* printer);
+  void GenerateMainParseLoop(io::Printer* printer, bool use_parse_context);
 
   int GetPresenceIndex(const FieldDescriptor* descriptor);
   FieldGeneratorBase* CreateFieldGeneratorInternal(
diff --git a/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.cc b/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.cc
index aae7091..402e44c 100644
--- a/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.cc
@@ -78,9 +78,15 @@
 }
 
 void RepeatedEnumFieldGenerator::GenerateParsingCode(io::Printer* printer) {
+  GenerateParsingCode(printer, true);
+}
+
+void RepeatedEnumFieldGenerator::GenerateParsingCode(io::Printer* printer, bool use_parse_context) {
   printer->Print(
     variables_,
-    "$name$_.AddEntriesFrom(ref input, _repeated_$name$_codec);\n");
+    use_parse_context
+    ? "$name$_.AddEntriesFrom(ref input, _repeated_$name$_codec);\n"
+    : "$name$_.AddEntriesFrom(input, _repeated_$name$_codec);\n");
 }
 
 void RepeatedEnumFieldGenerator::GenerateSerializationCode(io::Printer* printer) {
diff --git a/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.h b/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.h
index c7a632a..4ce13e6 100644
--- a/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.h
+++ b/src/google/protobuf/compiler/csharp/csharp_repeated_enum_field.h
@@ -59,6 +59,7 @@
   virtual void GenerateMembers(io::Printer* printer);
   virtual void GenerateMergingCode(io::Printer* printer);
   virtual void GenerateParsingCode(io::Printer* printer);
+  virtual void GenerateParsingCode(io::Printer* printer, bool use_parse_context);
   virtual void GenerateSerializationCode(io::Printer* printer);
   virtual void GenerateSerializedSizeCode(io::Printer* printer);
   virtual void GenerateExtensionCode(io::Printer* printer);
diff --git a/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.cc b/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.cc
index 2e2cfa8..4483740 100644
--- a/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.cc
@@ -93,9 +93,15 @@
 }
 
 void RepeatedMessageFieldGenerator::GenerateParsingCode(io::Printer* printer) {
+  GenerateParsingCode(printer, true);
+}
+
+void RepeatedMessageFieldGenerator::GenerateParsingCode(io::Printer* printer, bool use_parse_context) {
   printer->Print(
     variables_,
-    "$name$_.AddEntriesFrom(ref input, _repeated_$name$_codec);\n");
+    use_parse_context
+    ? "$name$_.AddEntriesFrom(ref input, _repeated_$name$_codec);\n"
+    : "$name$_.AddEntriesFrom(input, _repeated_$name$_codec);\n");
 }
 
 void RepeatedMessageFieldGenerator::GenerateSerializationCode(io::Printer* printer) {
diff --git a/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.h b/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.h
index 74f6874..2cf33a4 100644
--- a/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.h
+++ b/src/google/protobuf/compiler/csharp/csharp_repeated_message_field.h
@@ -59,6 +59,7 @@
   virtual void GenerateMembers(io::Printer* printer);
   virtual void GenerateMergingCode(io::Printer* printer);
   virtual void GenerateParsingCode(io::Printer* printer);
+  virtual void GenerateParsingCode(io::Printer* printer, bool use_parse_context);
   virtual void GenerateSerializationCode(io::Printer* printer);
   virtual void GenerateSerializedSizeCode(io::Printer* printer);
   virtual void GenerateExtensionCode(io::Printer* printer);
diff --git a/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.cc b/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.cc
index d4ff302..9231210 100644
--- a/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.cc
@@ -78,9 +78,15 @@
 }
 
 void RepeatedPrimitiveFieldGenerator::GenerateParsingCode(io::Printer* printer) {
+  GenerateParsingCode(printer, true);
+}
+
+void RepeatedPrimitiveFieldGenerator::GenerateParsingCode(io::Printer* printer, bool use_parse_context) {
   printer->Print(
     variables_,
-    "$name$_.AddEntriesFrom(ref input, _repeated_$name$_codec);\n");
+    use_parse_context
+    ? "$name$_.AddEntriesFrom(ref input, _repeated_$name$_codec);\n"
+    : "$name$_.AddEntriesFrom(input, _repeated_$name$_codec);\n");
 }
 
 void RepeatedPrimitiveFieldGenerator::GenerateSerializationCode(io::Printer* printer) {
diff --git a/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.h b/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.h
index 2a3be48..58db62d 100644
--- a/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.h
+++ b/src/google/protobuf/compiler/csharp/csharp_repeated_primitive_field.h
@@ -55,6 +55,7 @@
   virtual void GenerateMembers(io::Printer* printer);
   virtual void GenerateMergingCode(io::Printer* printer);
   virtual void GenerateParsingCode(io::Printer* printer);
+  virtual void GenerateParsingCode(io::Printer* printer, bool use_parse_context);
   virtual void GenerateSerializationCode(io::Printer* printer);
   virtual void GenerateSerializedSizeCode(io::Printer* printer);
   virtual void GenerateExtensionCode(io::Printer* printer);
diff --git a/src/google/protobuf/compiler/csharp/csharp_wrapper_field.cc b/src/google/protobuf/compiler/csharp/csharp_wrapper_field.cc
index cada81c..24381dd 100644
--- a/src/google/protobuf/compiler/csharp/csharp_wrapper_field.cc
+++ b/src/google/protobuf/compiler/csharp/csharp_wrapper_field.cc
@@ -114,12 +114,21 @@
 }
 
 void WrapperFieldGenerator::GenerateParsingCode(io::Printer* printer) {
+  GenerateParsingCode(printer, true);
+}
+
+void WrapperFieldGenerator::GenerateParsingCode(io::Printer* printer, bool use_parse_context) {
   printer->Print(
     variables_,
-    "$type_name$ value = _single_$name$_codec.Read(ref input);\n"
-    "if ($has_not_property_check$ || value != $default_value$) {\n"
-    "  $property_name$ = value;\n"
-    "}\n");
+    use_parse_context
+    ? "$type_name$ value = _single_$name$_codec.Read(ref input);\n"
+      "if ($has_not_property_check$ || value != $default_value$) {\n"
+      "  $property_name$ = value;\n"
+      "}\n"
+    : "$type_name$ value = _single_$name$_codec.Read(input);\n"
+      "if ($has_not_property_check$ || value != $default_value$) {\n"
+      "  $property_name$ = value;\n"
+      "}\n");
 }
 
 void WrapperFieldGenerator::GenerateSerializationCode(io::Printer* printer) {
@@ -248,9 +257,15 @@
 }
 
 void WrapperOneofFieldGenerator::GenerateParsingCode(io::Printer* printer) {
+  GenerateParsingCode(printer, true);
+}
+
+void WrapperOneofFieldGenerator::GenerateParsingCode(io::Printer* printer, bool use_parse_context) {
   printer->Print(
     variables_,
-    "$property_name$ = _oneof_$name$_codec.Read(ref input);\n");
+    use_parse_context
+    ? "$property_name$ = _oneof_$name$_codec.Read(ref input);\n"
+    : "$property_name$ = _oneof_$name$_codec.Read(input);\n");
 }
 
 void WrapperOneofFieldGenerator::GenerateSerializationCode(io::Printer* printer) {
diff --git a/src/google/protobuf/compiler/csharp/csharp_wrapper_field.h b/src/google/protobuf/compiler/csharp/csharp_wrapper_field.h
index 394e27d..438080d 100644
--- a/src/google/protobuf/compiler/csharp/csharp_wrapper_field.h
+++ b/src/google/protobuf/compiler/csharp/csharp_wrapper_field.h
@@ -58,6 +58,7 @@
   virtual void GenerateMembers(io::Printer* printer);
   virtual void GenerateMergingCode(io::Printer* printer);
   virtual void GenerateParsingCode(io::Printer* printer);
+  virtual void GenerateParsingCode(io::Printer* printer, bool use_parse_context);
   virtual void GenerateSerializationCode(io::Printer* printer);
   virtual void GenerateSerializedSizeCode(io::Printer* printer);
   virtual void GenerateExtensionCode(io::Printer* printer);
@@ -83,6 +84,7 @@
   virtual void GenerateMembers(io::Printer* printer);
   virtual void GenerateMergingCode(io::Printer* printer);
   virtual void GenerateParsingCode(io::Printer* printer);
+  virtual void GenerateParsingCode(io::Printer* printer, bool use_parse_context);
   virtual void GenerateSerializationCode(io::Printer* printer);
   virtual void GenerateSerializedSizeCode(io::Printer* printer);
 };
diff --git a/src/google/protobuf/compiler/main.cc b/src/google/protobuf/compiler/main.cc
index 5239e09..a702ca9 100644
--- a/src/google/protobuf/compiler/main.cc
+++ b/src/google/protobuf/compiler/main.cc
@@ -28,8 +28,6 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Author: kenton@google.com (Kenton Varda)
-
 #include <google/protobuf/compiler/cpp/cpp_generator.h>
 #include <google/protobuf/compiler/java/java_generator.h>
 #include <google/protobuf/compiler/js/js_generator.h>
@@ -87,10 +85,10 @@
   cli.RegisterGenerator("--csharp_out", "--csharp_opt", &csharp_generator,
                         "Generate C# source file.");
 
-  // Objective C
+  // Objective-C
   objectivec::ObjectiveCGenerator objc_generator;
   cli.RegisterGenerator("--objc_out", "--objc_opt", &objc_generator,
-                        "Generate Objective C header and source.");
+                        "Generate Objective-C header and source.");
 
   // JavaScript
   js::Generator js_generator;
diff --git a/src/google/protobuf/compiler/objectivec/objectivec_file.cc b/src/google/protobuf/compiler/objectivec/objectivec_file.cc
index 04733ca..58ca9c1 100644
--- a/src/google/protobuf/compiler/objectivec/objectivec_file.cc
+++ b/src/google/protobuf/compiler/objectivec/objectivec_file.cc
@@ -209,15 +209,15 @@
 FileGenerator::~FileGenerator() {}
 
 void FileGenerator::GenerateHeader(io::Printer *printer) {
-  std::set<string> headers;
+  std::vector<string> headers;
   // Generated files bundled with the library get minimal imports, everything
   // else gets the wrapper so everything is usable.
   if (is_bundled_proto_) {
-    headers.insert("GPBRootObject.h");
-    headers.insert("GPBMessage.h");
-    headers.insert("GPBDescriptor.h");
+    headers.push_back("GPBDescriptor.h");
+    headers.push_back("GPBMessage.h");
+    headers.push_back("GPBRootObject.h");
   } else {
-    headers.insert("GPBProtocolBuffers.h");
+    headers.push_back("GPBProtocolBuffers.h");
   }
   PrintFileRuntimePreamble(printer, headers);
 
@@ -242,6 +242,7 @@
     ImportWriter import_writer(
         options_.generate_for_named_framework,
         options_.named_framework_to_proto_path_mappings_path,
+        options_.runtime_import_prefix,
         is_bundled_proto_);
     const string header_extension(kHeaderExtension);
     for (int i = 0; i < file_->public_dependency_count(); i++) {
@@ -337,8 +338,8 @@
 
 void FileGenerator::GenerateSource(io::Printer *printer) {
   // #import the runtime support.
-  std::set<string> headers;
-  headers.insert("GPBProtocolBuffers_RuntimeSupport.h");
+  std::vector<string> headers;
+  headers.push_back("GPBProtocolBuffers_RuntimeSupport.h");
   PrintFileRuntimePreamble(printer, headers);
 
   // Enums use atomic in the generated code, so add the system import as needed.
@@ -355,6 +356,7 @@
     ImportWriter import_writer(
         options_.generate_for_named_framework,
         options_.named_framework_to_proto_path_mappings_path,
+        options_.runtime_import_prefix,
         is_bundled_proto_);
     const string header_extension(kHeaderExtension);
 
@@ -590,48 +592,15 @@
 // files. This currently only supports the runtime coming from a framework
 // as defined by the official CocoaPod.
 void FileGenerator::PrintFileRuntimePreamble(
-    io::Printer* printer, const std::set<string>& headers_to_import) const {
+    io::Printer* printer, const std::vector<string>& headers_to_import) const {
   printer->Print(
       "// Generated by the protocol buffer compiler.  DO NOT EDIT!\n"
       "// source: $filename$\n"
       "\n",
       "filename", file_->name());
-
-  const string framework_name(ProtobufLibraryFrameworkName);
-  const string cpp_symbol(ProtobufFrameworkImportSymbol(framework_name));
-
-  printer->Print(
-      "// This CPP symbol can be defined to use imports that match up to the framework\n"
-      "// imports needed when using CocoaPods.\n"
-      "#if !defined($cpp_symbol$)\n"
-      " #define $cpp_symbol$ 0\n"
-      "#endif\n"
-      "\n"
-      "#if $cpp_symbol$\n",
-      "cpp_symbol", cpp_symbol);
-
-
-  for (std::set<string>::const_iterator iter = headers_to_import.begin();
-       iter != headers_to_import.end(); ++iter) {
-    printer->Print(
-        " #import <$framework_name$/$header$>\n",
-        "header", *iter,
-        "framework_name", framework_name);
-  }
-
-  printer->Print(
-      "#else\n");
-
-  for (std::set<string>::const_iterator iter = headers_to_import.begin();
-       iter != headers_to_import.end(); ++iter) {
-    printer->Print(
-        " #import \"$header$\"\n",
-        "header", *iter);
-  }
-
-  printer->Print(
-      "#endif\n"
-      "\n");
+  ImportWriter::PrintRuntimeImports(
+      printer, headers_to_import, options_.runtime_import_prefix, true);
+  printer->Print("\n");
 }
 
 }  // namespace objectivec
diff --git a/src/google/protobuf/compiler/objectivec/objectivec_file.h b/src/google/protobuf/compiler/objectivec/objectivec_file.h
index fd57263..258bd13 100644
--- a/src/google/protobuf/compiler/objectivec/objectivec_file.h
+++ b/src/google/protobuf/compiler/objectivec/objectivec_file.h
@@ -72,7 +72,7 @@
   const Options options_;
 
   void PrintFileRuntimePreamble(
-      io::Printer* printer, const std::set<string>& headers_to_import) const;
+      io::Printer* printer, const std::vector<string>& headers_to_import) const;
 };
 
 }  // namespace objectivec
diff --git a/src/google/protobuf/compiler/objectivec/objectivec_generator.cc b/src/google/protobuf/compiler/objectivec/objectivec_generator.cc
index 25338ad..257e4f9 100644
--- a/src/google/protobuf/compiler/objectivec/objectivec_generator.cc
+++ b/src/google/protobuf/compiler/objectivec/objectivec_generator.cc
@@ -127,6 +127,13 @@
       // with generate_for_named_framework, or the relative path to it's include
       // path otherwise.
       generation_options.named_framework_to_proto_path_mappings_path = options[i].second;
+    } else if (options[i].first == "runtime_import_prefix") {
+      // Path to use as a prefix on #imports of runtime provided headers in the
+      // generated files. When integrating ObjC protos into a build system,
+      // this can be used to avoid having to add the runtime directory to the
+      // header search path since the generate #import will be more complete.
+      generation_options.runtime_import_prefix =
+          StripSuffixString(options[i].second, "/");
     } else {
       *error = "error: Unknown generator option: " + options[i].first;
       return false;
diff --git a/src/google/protobuf/compiler/objectivec/objectivec_generator.h b/src/google/protobuf/compiler/objectivec/objectivec_generator.h
index b09e2b2..d1e490c 100644
--- a/src/google/protobuf/compiler/objectivec/objectivec_generator.h
+++ b/src/google/protobuf/compiler/objectivec/objectivec_generator.h
@@ -67,7 +67,7 @@
                    GeneratorContext* context,
                    string* error) const override;
 
-  uint64 GetSupportedFeatures() const override {
+  uint64_t GetSupportedFeatures() const override {
     return FEATURE_PROTO3_OPTIONAL;
   }
 };
diff --git a/src/google/protobuf/compiler/objectivec/objectivec_helpers.cc b/src/google/protobuf/compiler/objectivec/objectivec_helpers.cc
index df11689..8b2b719 100644
--- a/src/google/protobuf/compiler/objectivec/objectivec_helpers.cc
+++ b/src/google/protobuf/compiler/objectivec/objectivec_helpers.cc
@@ -1566,10 +1566,12 @@
 ImportWriter::ImportWriter(
   const string& generate_for_named_framework,
   const string& named_framework_to_proto_path_mappings_path,
+  const string& runtime_import_prefix,
   bool include_wkt_imports)
     : generate_for_named_framework_(generate_for_named_framework),
       named_framework_to_proto_path_mappings_path_(
           named_framework_to_proto_path_mappings_path),
+      runtime_import_prefix_(runtime_import_prefix),
       include_wkt_imports_(include_wkt_imports),
       need_to_parse_mapping_file_(true) {
 }
@@ -1585,8 +1587,7 @@
     if (include_wkt_imports_) {
       const string header_name =
         "GPB" + FilePathBasename(file) + header_extension;
-      protobuf_framework_imports_.push_back(header_name);
-      protobuf_non_framework_imports_.push_back(header_name);
+      protobuf_imports_.push_back(header_name);
     }
     return;
   }
@@ -1616,36 +1617,10 @@
 }
 
 void ImportWriter::Print(io::Printer* printer) const {
-  assert(protobuf_non_framework_imports_.size() ==
-         protobuf_framework_imports_.size());
-
   bool add_blank_line = false;
 
-  if (!protobuf_framework_imports_.empty()) {
-    const string framework_name(ProtobufLibraryFrameworkName);
-    const string cpp_symbol(ProtobufFrameworkImportSymbol(framework_name));
-
-    printer->Print(
-        "#if $cpp_symbol$\n",
-        "cpp_symbol", cpp_symbol);
-    for (std::vector<string>::const_iterator iter = protobuf_framework_imports_.begin();
-         iter != protobuf_framework_imports_.end(); ++iter) {
-      printer->Print(
-          " #import <$framework_name$/$header$>\n",
-          "framework_name", framework_name,
-          "header", *iter);
-    }
-    printer->Print(
-        "#else\n");
-    for (std::vector<string>::const_iterator iter = protobuf_non_framework_imports_.begin();
-         iter != protobuf_non_framework_imports_.end(); ++iter) {
-      printer->Print(
-          " #import \"$header$\"\n",
-          "header", *iter);
-    }
-    printer->Print(
-        "#endif\n");
-
+  if (!protobuf_imports_.empty()) {
+    PrintRuntimeImports(printer, protobuf_imports_, runtime_import_prefix_);
     add_blank_line = true;
   }
 
@@ -1678,6 +1653,57 @@
   }
 }
 
+void ImportWriter::PrintRuntimeImports(
+    io::Printer* printer,
+    const std::vector<string>& header_to_import,
+    const string& runtime_import_prefix,
+    bool default_cpp_symbol) {
+
+  // Given an override, use that.
+  if (!runtime_import_prefix.empty()) {
+    for (const auto& header : header_to_import) {
+      printer->Print(
+          " #import \"$import_prefix$/$header$\"\n",
+          "import_prefix", runtime_import_prefix,
+          "header", header);
+    }
+    return;
+  }
+
+  const string framework_name(ProtobufLibraryFrameworkName);
+  const string cpp_symbol(ProtobufFrameworkImportSymbol(framework_name));
+
+  if (default_cpp_symbol) {
+    printer->Print(
+        "// This CPP symbol can be defined to use imports that match up to the framework\n"
+        "// imports needed when using CocoaPods.\n"
+        "#if !defined($cpp_symbol$)\n"
+        " #define $cpp_symbol$ 0\n"
+        "#endif\n"
+        "\n",
+        "cpp_symbol", cpp_symbol);
+  }
+
+  printer->Print(
+      "#if $cpp_symbol$\n",
+      "cpp_symbol", cpp_symbol);
+  for (const auto& header : header_to_import) {
+    printer->Print(
+        " #import <$framework_name$/$header$>\n",
+        "framework_name", framework_name,
+        "header", header);
+  }
+  printer->Print(
+      "#else\n");
+  for (const auto& header : header_to_import) {
+    printer->Print(
+        " #import \"$header$\"\n",
+        "header", header);
+  }
+  printer->Print(
+      "#endif\n");
+}
+
 void ImportWriter::ParseFrameworkMappings() {
   need_to_parse_mapping_file_ = false;
   if (named_framework_to_proto_path_mappings_path_.empty()) {
diff --git a/src/google/protobuf/compiler/objectivec/objectivec_helpers.h b/src/google/protobuf/compiler/objectivec/objectivec_helpers.h
index 5f91f4e..02f540f 100644
--- a/src/google/protobuf/compiler/objectivec/objectivec_helpers.h
+++ b/src/google/protobuf/compiler/objectivec/objectivec_helpers.h
@@ -53,6 +53,7 @@
   std::vector<string> expected_prefixes_suppressions;
   string generate_for_named_framework;
   string named_framework_to_proto_path_mappings_path;
+  string runtime_import_prefix;
 };
 
 // Escape C++ trigraphs by escaping question marks to "\?".
@@ -279,12 +280,18 @@
  public:
   ImportWriter(const string& generate_for_named_framework,
                const string& named_framework_to_proto_path_mappings_path,
+               const string& runtime_import_prefix,
                bool include_wkt_imports);
   ~ImportWriter();
 
   void AddFile(const FileDescriptor* file, const string& header_extension);
   void Print(io::Printer *printer) const;
 
+  static void PrintRuntimeImports(io::Printer *printer,
+                                  const std::vector<string>& header_to_import,
+                                  const string& runtime_import_prefix,
+                                  bool default_cpp_symbol = false);
+
  private:
   class ProtoFrameworkCollector : public LineConsumer {
    public:
@@ -301,12 +308,12 @@
 
   const string generate_for_named_framework_;
   const string named_framework_to_proto_path_mappings_path_;
+  const string runtime_import_prefix_;
   const bool include_wkt_imports_;
   std::map<string, string> proto_file_to_framework_name_;
   bool need_to_parse_mapping_file_;
 
-  std::vector<string> protobuf_framework_imports_;
-  std::vector<string> protobuf_non_framework_imports_;
+  std::vector<string> protobuf_imports_;
   std::vector<string> other_framework_imports_;
   std::vector<string> other_imports_;
 };
diff --git a/src/google/protobuf/compiler/plugin.pb.h b/src/google/protobuf/compiler/plugin.pb.h
index f4a0449..186be67 100644
--- a/src/google/protobuf/compiler/plugin.pb.h
+++ b/src/google/protobuf/compiler/plugin.pb.h
@@ -115,7 +115,7 @@
 class PROTOC_EXPORT Version PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.compiler.Version) */ {
  public:
-  inline Version() : Version(nullptr) {};
+  inline Version() : Version(nullptr) {}
   virtual ~Version();
 
   Version(const Version& from);
@@ -316,7 +316,7 @@
 class PROTOC_EXPORT CodeGeneratorRequest PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.compiler.CodeGeneratorRequest) */ {
  public:
-  inline CodeGeneratorRequest() : CodeGeneratorRequest(nullptr) {};
+  inline CodeGeneratorRequest() : CodeGeneratorRequest(nullptr) {}
   virtual ~CodeGeneratorRequest();
 
   CodeGeneratorRequest(const CodeGeneratorRequest& from);
@@ -538,7 +538,7 @@
 class PROTOC_EXPORT CodeGeneratorResponse_File PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.compiler.CodeGeneratorResponse.File) */ {
  public:
-  inline CodeGeneratorResponse_File() : CodeGeneratorResponse_File(nullptr) {};
+  inline CodeGeneratorResponse_File() : CodeGeneratorResponse_File(nullptr) {}
   virtual ~CodeGeneratorResponse_File();
 
   CodeGeneratorResponse_File(const CodeGeneratorResponse_File& from);
@@ -738,7 +738,7 @@
 class PROTOC_EXPORT CodeGeneratorResponse PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.compiler.CodeGeneratorResponse) */ {
  public:
-  inline CodeGeneratorResponse() : CodeGeneratorResponse(nullptr) {};
+  inline CodeGeneratorResponse() : CodeGeneratorResponse(nullptr) {}
   virtual ~CodeGeneratorResponse();
 
   CodeGeneratorResponse(const CodeGeneratorResponse& from);
diff --git a/src/google/protobuf/compiler/python/python_generator.cc b/src/google/protobuf/compiler/python/python_generator.cc
index a95b37f..b4beda6 100644
--- a/src/google/protobuf/compiler/python/python_generator.cc
+++ b/src/google/protobuf/compiler/python/python_generator.cc
@@ -106,11 +106,12 @@
 
 // Keywords reserved by the Python language.
 const char* const kKeywords[] = {
-    "False",   "None",     "True",     "and",    "as",    "assert", "break",
-    "class",   "continue", "def",      "del",    "elif",  "else",   "except",
-    "finally", "for",      "from",     "global", "if",    "import", "in",
-    "is",      "lambda",   "nonlocal", "not",    "or",    "pass",   "raise",
-    "return",  "try",      "while",    "with",   "yield", "print",
+    "False",  "None",     "True",  "and",    "as",       "assert",
+    "async",  "await",    "break", "class",  "continue", "def",
+    "del",    "elif",     "else",  "except", "finally",  "for",
+    "from",   "global",   "if",    "import", "in",       "is",
+    "lambda", "nonlocal", "not",   "or",     "pass",     "raise",
+    "return", "try",      "while", "with",   "yield",    "print",
 };
 const char* const* kKeywordsEnd =
     kKeywords + (sizeof(kKeywords) / sizeof(kKeywords[0]));
diff --git a/src/google/protobuf/compiler/ruby/ruby_generator.h b/src/google/protobuf/compiler/ruby/ruby_generator.h
index ea4f30a..b40fcd0 100644
--- a/src/google/protobuf/compiler/ruby/ruby_generator.h
+++ b/src/google/protobuf/compiler/ruby/ruby_generator.h
@@ -52,7 +52,7 @@
   bool Generate(const FileDescriptor* file, const string& parameter,
                 GeneratorContext* generator_context,
                 string* error) const override;
-  uint64 GetSupportedFeatures() const override {
+  uint64_t GetSupportedFeatures() const override {
     return FEATURE_PROTO3_OPTIONAL;
   }
 };
diff --git a/src/google/protobuf/descriptor.pb.h b/src/google/protobuf/descriptor.pb.h
index fd0ed66..49a6f05 100644
--- a/src/google/protobuf/descriptor.pb.h
+++ b/src/google/protobuf/descriptor.pb.h
@@ -333,7 +333,7 @@
 class PROTOBUF_EXPORT FileDescriptorSet PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.FileDescriptorSet) */ {
  public:
-  inline FileDescriptorSet() : FileDescriptorSet(nullptr) {};
+  inline FileDescriptorSet() : FileDescriptorSet(nullptr) {}
   virtual ~FileDescriptorSet();
 
   FileDescriptorSet(const FileDescriptorSet& from);
@@ -486,7 +486,7 @@
 class PROTOBUF_EXPORT FileDescriptorProto PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.FileDescriptorProto) */ {
  public:
-  inline FileDescriptorProto() : FileDescriptorProto(nullptr) {};
+  inline FileDescriptorProto() : FileDescriptorProto(nullptr) {}
   virtual ~FileDescriptorProto();
 
   FileDescriptorProto(const FileDescriptorProto& from);
@@ -880,7 +880,7 @@
 class PROTOBUF_EXPORT DescriptorProto_ExtensionRange PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.DescriptorProto.ExtensionRange) */ {
  public:
-  inline DescriptorProto_ExtensionRange() : DescriptorProto_ExtensionRange(nullptr) {};
+  inline DescriptorProto_ExtensionRange() : DescriptorProto_ExtensionRange(nullptr) {}
   virtual ~DescriptorProto_ExtensionRange();
 
   DescriptorProto_ExtensionRange(const DescriptorProto_ExtensionRange& from);
@@ -1064,7 +1064,7 @@
 class PROTOBUF_EXPORT DescriptorProto_ReservedRange PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.DescriptorProto.ReservedRange) */ {
  public:
-  inline DescriptorProto_ReservedRange() : DescriptorProto_ReservedRange(nullptr) {};
+  inline DescriptorProto_ReservedRange() : DescriptorProto_ReservedRange(nullptr) {}
   virtual ~DescriptorProto_ReservedRange();
 
   DescriptorProto_ReservedRange(const DescriptorProto_ReservedRange& from);
@@ -1228,7 +1228,7 @@
 class PROTOBUF_EXPORT DescriptorProto PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.DescriptorProto) */ {
  public:
-  inline DescriptorProto() : DescriptorProto(nullptr) {};
+  inline DescriptorProto() : DescriptorProto(nullptr) {}
   virtual ~DescriptorProto();
 
   DescriptorProto(const DescriptorProto& from);
@@ -1573,7 +1573,7 @@
 class PROTOBUF_EXPORT ExtensionRangeOptions PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.ExtensionRangeOptions) */ {
  public:
-  inline ExtensionRangeOptions() : ExtensionRangeOptions(nullptr) {};
+  inline ExtensionRangeOptions() : ExtensionRangeOptions(nullptr) {}
   virtual ~ExtensionRangeOptions();
 
   ExtensionRangeOptions(const ExtensionRangeOptions& from);
@@ -1729,7 +1729,7 @@
 class PROTOBUF_EXPORT FieldDescriptorProto PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.FieldDescriptorProto) */ {
  public:
-  inline FieldDescriptorProto() : FieldDescriptorProto(nullptr) {};
+  inline FieldDescriptorProto() : FieldDescriptorProto(nullptr) {}
   virtual ~FieldDescriptorProto();
 
   FieldDescriptorProto(const FieldDescriptorProto& from);
@@ -2162,7 +2162,7 @@
 class PROTOBUF_EXPORT OneofDescriptorProto PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.OneofDescriptorProto) */ {
  public:
-  inline OneofDescriptorProto() : OneofDescriptorProto(nullptr) {};
+  inline OneofDescriptorProto() : OneofDescriptorProto(nullptr) {}
   virtual ~OneofDescriptorProto();
 
   OneofDescriptorProto(const OneofDescriptorProto& from);
@@ -2338,7 +2338,7 @@
 class PROTOBUF_EXPORT EnumDescriptorProto_EnumReservedRange PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.EnumDescriptorProto.EnumReservedRange) */ {
  public:
-  inline EnumDescriptorProto_EnumReservedRange() : EnumDescriptorProto_EnumReservedRange(nullptr) {};
+  inline EnumDescriptorProto_EnumReservedRange() : EnumDescriptorProto_EnumReservedRange(nullptr) {}
   virtual ~EnumDescriptorProto_EnumReservedRange();
 
   EnumDescriptorProto_EnumReservedRange(const EnumDescriptorProto_EnumReservedRange& from);
@@ -2502,7 +2502,7 @@
 class PROTOBUF_EXPORT EnumDescriptorProto PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.EnumDescriptorProto) */ {
  public:
-  inline EnumDescriptorProto() : EnumDescriptorProto(nullptr) {};
+  inline EnumDescriptorProto() : EnumDescriptorProto(nullptr) {}
   virtual ~EnumDescriptorProto();
 
   EnumDescriptorProto(const EnumDescriptorProto& from);
@@ -2746,7 +2746,7 @@
 class PROTOBUF_EXPORT EnumValueDescriptorProto PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.EnumValueDescriptorProto) */ {
  public:
-  inline EnumValueDescriptorProto() : EnumValueDescriptorProto(nullptr) {};
+  inline EnumValueDescriptorProto() : EnumValueDescriptorProto(nullptr) {}
   virtual ~EnumValueDescriptorProto();
 
   EnumValueDescriptorProto(const EnumValueDescriptorProto& from);
@@ -2937,7 +2937,7 @@
 class PROTOBUF_EXPORT ServiceDescriptorProto PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.ServiceDescriptorProto) */ {
  public:
-  inline ServiceDescriptorProto() : ServiceDescriptorProto(nullptr) {};
+  inline ServiceDescriptorProto() : ServiceDescriptorProto(nullptr) {}
   virtual ~ServiceDescriptorProto();
 
   ServiceDescriptorProto(const ServiceDescriptorProto& from);
@@ -3133,7 +3133,7 @@
 class PROTOBUF_EXPORT MethodDescriptorProto PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.MethodDescriptorProto) */ {
  public:
-  inline MethodDescriptorProto() : MethodDescriptorProto(nullptr) {};
+  inline MethodDescriptorProto() : MethodDescriptorProto(nullptr) {}
   virtual ~MethodDescriptorProto();
 
   MethodDescriptorProto(const MethodDescriptorProto& from);
@@ -3383,7 +3383,7 @@
 class PROTOBUF_EXPORT FileOptions PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.FileOptions) */ {
  public:
-  inline FileOptions() : FileOptions(nullptr) {};
+  inline FileOptions() : FileOptions(nullptr) {}
   virtual ~FileOptions();
 
   FileOptions(const FileOptions& from);
@@ -3942,7 +3942,7 @@
 class PROTOBUF_EXPORT MessageOptions PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.MessageOptions) */ {
  public:
-  inline MessageOptions() : MessageOptions(nullptr) {};
+  inline MessageOptions() : MessageOptions(nullptr) {}
   virtual ~MessageOptions();
 
   MessageOptions(const MessageOptions& from);
@@ -4159,7 +4159,7 @@
 class PROTOBUF_EXPORT FieldOptions PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.FieldOptions) */ {
  public:
-  inline FieldOptions() : FieldOptions(nullptr) {};
+  inline FieldOptions() : FieldOptions(nullptr) {}
   virtual ~FieldOptions();
 
   FieldOptions(const FieldOptions& from);
@@ -4470,7 +4470,7 @@
 class PROTOBUF_EXPORT OneofOptions PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.OneofOptions) */ {
  public:
-  inline OneofOptions() : OneofOptions(nullptr) {};
+  inline OneofOptions() : OneofOptions(nullptr) {}
   virtual ~OneofOptions();
 
   OneofOptions(const OneofOptions& from);
@@ -4626,7 +4626,7 @@
 class PROTOBUF_EXPORT EnumOptions PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.EnumOptions) */ {
  public:
-  inline EnumOptions() : EnumOptions(nullptr) {};
+  inline EnumOptions() : EnumOptions(nullptr) {}
   virtual ~EnumOptions();
 
   EnumOptions(const EnumOptions& from);
@@ -4813,7 +4813,7 @@
 class PROTOBUF_EXPORT EnumValueOptions PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.EnumValueOptions) */ {
  public:
-  inline EnumValueOptions() : EnumValueOptions(nullptr) {};
+  inline EnumValueOptions() : EnumValueOptions(nullptr) {}
   virtual ~EnumValueOptions();
 
   EnumValueOptions(const EnumValueOptions& from);
@@ -4985,7 +4985,7 @@
 class PROTOBUF_EXPORT ServiceOptions PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.ServiceOptions) */ {
  public:
-  inline ServiceOptions() : ServiceOptions(nullptr) {};
+  inline ServiceOptions() : ServiceOptions(nullptr) {}
   virtual ~ServiceOptions();
 
   ServiceOptions(const ServiceOptions& from);
@@ -5157,7 +5157,7 @@
 class PROTOBUF_EXPORT MethodOptions PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.MethodOptions) */ {
  public:
-  inline MethodOptions() : MethodOptions(nullptr) {};
+  inline MethodOptions() : MethodOptions(nullptr) {}
   virtual ~MethodOptions();
 
   MethodOptions(const MethodOptions& from);
@@ -5376,7 +5376,7 @@
 class PROTOBUF_EXPORT UninterpretedOption_NamePart PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.UninterpretedOption.NamePart) */ {
  public:
-  inline UninterpretedOption_NamePart() : UninterpretedOption_NamePart(nullptr) {};
+  inline UninterpretedOption_NamePart() : UninterpretedOption_NamePart(nullptr) {}
   virtual ~UninterpretedOption_NamePart();
 
   UninterpretedOption_NamePart(const UninterpretedOption_NamePart& from);
@@ -5550,7 +5550,7 @@
 class PROTOBUF_EXPORT UninterpretedOption PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.UninterpretedOption) */ {
  public:
-  inline UninterpretedOption() : UninterpretedOption(nullptr) {};
+  inline UninterpretedOption() : UninterpretedOption(nullptr) {}
   virtual ~UninterpretedOption();
 
   UninterpretedOption(const UninterpretedOption& from);
@@ -5817,7 +5817,7 @@
 class PROTOBUF_EXPORT SourceCodeInfo_Location PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.SourceCodeInfo.Location) */ {
  public:
-  inline SourceCodeInfo_Location() : SourceCodeInfo_Location(nullptr) {};
+  inline SourceCodeInfo_Location() : SourceCodeInfo_Location(nullptr) {}
   virtual ~SourceCodeInfo_Location();
 
   SourceCodeInfo_Location(const SourceCodeInfo_Location& from);
@@ -6071,7 +6071,7 @@
 class PROTOBUF_EXPORT SourceCodeInfo PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.SourceCodeInfo) */ {
  public:
-  inline SourceCodeInfo() : SourceCodeInfo(nullptr) {};
+  inline SourceCodeInfo() : SourceCodeInfo(nullptr) {}
   virtual ~SourceCodeInfo();
 
   SourceCodeInfo(const SourceCodeInfo& from);
@@ -6226,7 +6226,7 @@
 class PROTOBUF_EXPORT GeneratedCodeInfo_Annotation PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.GeneratedCodeInfo.Annotation) */ {
  public:
-  inline GeneratedCodeInfo_Annotation() : GeneratedCodeInfo_Annotation(nullptr) {};
+  inline GeneratedCodeInfo_Annotation() : GeneratedCodeInfo_Annotation(nullptr) {}
   virtual ~GeneratedCodeInfo_Annotation();
 
   GeneratedCodeInfo_Annotation(const GeneratedCodeInfo_Annotation& from);
@@ -6437,7 +6437,7 @@
 class PROTOBUF_EXPORT GeneratedCodeInfo PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.GeneratedCodeInfo) */ {
  public:
-  inline GeneratedCodeInfo() : GeneratedCodeInfo(nullptr) {};
+  inline GeneratedCodeInfo() : GeneratedCodeInfo(nullptr) {}
   virtual ~GeneratedCodeInfo();
 
   GeneratedCodeInfo(const GeneratedCodeInfo& from);
diff --git a/src/google/protobuf/duration.pb.h b/src/google/protobuf/duration.pb.h
index 675cb93..685e123 100644
--- a/src/google/protobuf/duration.pb.h
+++ b/src/google/protobuf/duration.pb.h
@@ -69,7 +69,7 @@
 class PROTOBUF_EXPORT Duration PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Duration) */ {
  public:
-  inline Duration() : Duration(nullptr) {};
+  inline Duration() : Duration(nullptr) {}
   virtual ~Duration();
 
   Duration(const Duration& from);
diff --git a/src/google/protobuf/empty.pb.h b/src/google/protobuf/empty.pb.h
index 232c194..88d0794 100644
--- a/src/google/protobuf/empty.pb.h
+++ b/src/google/protobuf/empty.pb.h
@@ -69,7 +69,7 @@
 class PROTOBUF_EXPORT Empty PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Empty) */ {
  public:
-  inline Empty() : Empty(nullptr) {};
+  inline Empty() : Empty(nullptr) {}
   virtual ~Empty();
 
   Empty(const Empty& from);
diff --git a/src/google/protobuf/field_mask.pb.h b/src/google/protobuf/field_mask.pb.h
index b32ae3f..2d876c7 100644
--- a/src/google/protobuf/field_mask.pb.h
+++ b/src/google/protobuf/field_mask.pb.h
@@ -69,7 +69,7 @@
 class PROTOBUF_EXPORT FieldMask PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.FieldMask) */ {
  public:
-  inline FieldMask() : FieldMask(nullptr) {};
+  inline FieldMask() : FieldMask(nullptr) {}
   virtual ~FieldMask();
 
   FieldMask(const FieldMask& from);
diff --git a/src/google/protobuf/map_entry_lite.h b/src/google/protobuf/map_entry_lite.h
index 7125ba1..161d08d 100644
--- a/src/google/protobuf/map_entry_lite.h
+++ b/src/google/protobuf/map_entry_lite.h
@@ -266,13 +266,8 @@
 
   size_t ByteSizeLong() const override {
     size_t size = 0;
-    size += has_key() ? kTagSize +
-                            static_cast<size_t>(KeyTypeHandler::ByteSize(key()))
-                      : 0;
-    size += has_value()
-                ? kTagSize +
-                      static_cast<size_t>(ValueTypeHandler::ByteSize(value()))
-                : 0;
+    size += kTagSize + static_cast<size_t>(KeyTypeHandler::ByteSize(key()));
+    size += kTagSize + static_cast<size_t>(ValueTypeHandler::ByteSize(value()));
     return size;
   }
 
diff --git a/src/google/protobuf/map_type_handler.h b/src/google/protobuf/map_type_handler.h
index 5efc6fb..d54aa22 100644
--- a/src/google/protobuf/map_type_handler.h
+++ b/src/google/protobuf/map_type_handler.h
@@ -240,7 +240,7 @@
                                                int default_enum);             \
     static inline size_t SpaceUsedInMapEntryLong(const TypeOnMemory& value);  \
     static inline size_t SpaceUsedInMapLong(const TypeOnMemory& value);       \
-    static inline size_t SpaceUsedInMapLong(const std::string& value);        \
+    static inline size_t SpaceUsedInMapLong(ConstStringParam value);          \
     static inline void AssignDefaultValue(TypeOnMemory* value);               \
     static inline const MapEntryAccessorType& DefaultIfNotInitialized(        \
         const TypeOnMemory& value, const TypeOnMemory& default_value);        \
@@ -643,8 +643,8 @@
   template <typename Type>                                                    \
   inline size_t                                                               \
   MapTypeHandler<WireFormatLite::TYPE_##FieldType, Type>::SpaceUsedInMapLong( \
-      const std::string& value) {                                             \
-    return sizeof(value);                                                     \
+      ConstStringParam value) {                                               \
+    return sizeof(std::string);                                               \
   }                                                                           \
   template <typename Type>                                                    \
   inline void MapTypeHandler<WireFormatLite::TYPE_##FieldType, Type>::Clear(  \
diff --git a/src/google/protobuf/repeated_field.h b/src/google/protobuf/repeated_field.h
index fd01a66..07800f5 100644
--- a/src/google/protobuf/repeated_field.h
+++ b/src/google/protobuf/repeated_field.h
@@ -439,43 +439,50 @@
   //
   // The first version executes at 7 cycles per iteration while the second
   // version near 1 or 2 cycles.
-  class FastAdder {
+  template <int = 0, bool = std::is_pod<Element>::value>
+  class FastAdderImpl {
    public:
-    explicit FastAdder(RepeatedField* rf) : repeated_field_(rf) {
-      if (kIsPod) {
-        index_ = repeated_field_->current_size_;
+    explicit FastAdderImpl(RepeatedField* rf) : repeated_field_(rf) {
+      index_ = repeated_field_->current_size_;
+      capacity_ = repeated_field_->total_size_;
+      buffer_ = repeated_field_->unsafe_elements();
+    }
+    ~FastAdderImpl() { repeated_field_->current_size_ = index_; }
+
+    void Add(Element val) {
+      if (index_ == capacity_) {
+        repeated_field_->current_size_ = index_;
+        repeated_field_->Reserve(index_ + 1);
         capacity_ = repeated_field_->total_size_;
         buffer_ = repeated_field_->unsafe_elements();
       }
-    }
-    ~FastAdder() {
-      if (kIsPod) repeated_field_->current_size_ = index_;
-    }
-
-    void Add(const Element& val) {
-      if (kIsPod) {
-        if (index_ == capacity_) {
-          repeated_field_->current_size_ = index_;
-          repeated_field_->Reserve(index_ + 1);
-          capacity_ = repeated_field_->total_size_;
-          buffer_ = repeated_field_->unsafe_elements();
-        }
-        buffer_[index_++] = val;
-      } else {
-        repeated_field_->Add(val);
-      }
+      buffer_[index_++] = val;
     }
 
    private:
-    constexpr static bool kIsPod = std::is_pod<Element>::value;
     RepeatedField* repeated_field_;
     int index_;
     int capacity_;
     Element* buffer_;
 
-    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FastAdder);
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FastAdderImpl);
   };
 
+  // FastAdder is a wrapper for adding fields. The specialization above handles
+  // POD types more efficiently than RepeatedField.
+  template <int I>
+  class FastAdderImpl<I, false> {
+   public:
+    explicit FastAdderImpl(RepeatedField* rf) : repeated_field_(rf) {}
+    void Add(const Element& val) { repeated_field_->Add(val); }
+
+   private:
+    RepeatedField* repeated_field_;
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FastAdderImpl);
+  };
+
+  using FastAdder = FastAdderImpl<>;
+
   friend class TestRepeatedFieldHelper;
   friend class ::google::protobuf::internal::ParseContext;
 };
@@ -1329,8 +1336,15 @@
 template <typename Element>
 inline void RepeatedField<Element>::Add(const Element& value) {
   uint32 size = current_size_;
-  if (static_cast<int>(size) == total_size_) Reserve(total_size_ + 1);
-  elements()[size] = value;
+  if (static_cast<int>(size) == total_size_) {
+    // value could reference an element of the array. Reserving new space will
+    // invalidate the reference. So we must make a copy first.
+    auto tmp = value;
+    Reserve(total_size_ + 1);
+    elements()[size] = std::move(tmp);
+  } else {
+    elements()[size] = value;
+  }
   current_size_ = size + 1;
 }
 
diff --git a/src/google/protobuf/repeated_field_unittest.cc b/src/google/protobuf/repeated_field_unittest.cc
index 3d64782..26b2384 100644
--- a/src/google/protobuf/repeated_field_unittest.cc
+++ b/src/google/protobuf/repeated_field_unittest.cc
@@ -807,6 +807,14 @@
   // strings.
 }
 
+TEST(RepeatedField, TestSAddFromSelf) {
+  RepeatedField<int> field;
+  field.Add(0);
+  for (int i = 0; i < 1000; i++) {
+    field.Add(field[0]);
+  }
+}
+
 // ===================================================================
 // RepeatedPtrField tests.  These pretty much just mirror the RepeatedField
 // tests above.
diff --git a/src/google/protobuf/source_context.pb.h b/src/google/protobuf/source_context.pb.h
index c0326de..b48860d 100644
--- a/src/google/protobuf/source_context.pb.h
+++ b/src/google/protobuf/source_context.pb.h
@@ -69,7 +69,7 @@
 class PROTOBUF_EXPORT SourceContext PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.SourceContext) */ {
  public:
-  inline SourceContext() : SourceContext(nullptr) {};
+  inline SourceContext() : SourceContext(nullptr) {}
   virtual ~SourceContext();
 
   SourceContext(const SourceContext& from);
diff --git a/src/google/protobuf/struct.pb.h b/src/google/protobuf/struct.pb.h
index c0fdf90..0c56821 100644
--- a/src/google/protobuf/struct.pb.h
+++ b/src/google/protobuf/struct.pb.h
@@ -141,7 +141,7 @@
 class PROTOBUF_EXPORT Struct PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Struct) */ {
  public:
-  inline Struct() : Struct(nullptr) {};
+  inline Struct() : Struct(nullptr) {}
   virtual ~Struct();
 
   Struct(const Struct& from);
@@ -292,7 +292,7 @@
 class PROTOBUF_EXPORT Value PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Value) */ {
  public:
-  inline Value() : Value(nullptr) {};
+  inline Value() : Value(nullptr) {}
   virtual ~Value();
 
   Value(const Value& from);
@@ -547,7 +547,7 @@
 class PROTOBUF_EXPORT ListValue PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.ListValue) */ {
  public:
-  inline ListValue() : ListValue(nullptr) {};
+  inline ListValue() : ListValue(nullptr) {}
   virtual ~ListValue();
 
   ListValue(const ListValue& from);
diff --git a/src/google/protobuf/timestamp.pb.h b/src/google/protobuf/timestamp.pb.h
index b3db098..687aafd 100644
--- a/src/google/protobuf/timestamp.pb.h
+++ b/src/google/protobuf/timestamp.pb.h
@@ -69,7 +69,7 @@
 class PROTOBUF_EXPORT Timestamp PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Timestamp) */ {
  public:
-  inline Timestamp() : Timestamp(nullptr) {};
+  inline Timestamp() : Timestamp(nullptr) {}
   virtual ~Timestamp();
 
   Timestamp(const Timestamp& from);
diff --git a/src/google/protobuf/type.pb.h b/src/google/protobuf/type.pb.h
index ea57370..302cd71 100644
--- a/src/google/protobuf/type.pb.h
+++ b/src/google/protobuf/type.pb.h
@@ -182,7 +182,7 @@
 class PROTOBUF_EXPORT Type PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Type) */ {
  public:
-  inline Type() : Type(nullptr) {};
+  inline Type() : Type(nullptr) {}
   virtual ~Type();
 
   Type(const Type& from);
@@ -423,7 +423,7 @@
 class PROTOBUF_EXPORT Field PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Field) */ {
  public:
-  inline Field() : Field(nullptr) {};
+  inline Field() : Field(nullptr) {}
   virtual ~Field();
 
   Field(const Field& from);
@@ -794,7 +794,7 @@
 class PROTOBUF_EXPORT Enum PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Enum) */ {
  public:
-  inline Enum() : Enum(nullptr) {};
+  inline Enum() : Enum(nullptr) {}
   virtual ~Enum();
 
   Enum(const Enum& from);
@@ -1009,7 +1009,7 @@
 class PROTOBUF_EXPORT EnumValue PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.EnumValue) */ {
  public:
-  inline EnumValue() : EnumValue(nullptr) {};
+  inline EnumValue() : EnumValue(nullptr) {}
   virtual ~EnumValue();
 
   EnumValue(const EnumValue& from);
@@ -1184,7 +1184,7 @@
 class PROTOBUF_EXPORT Option PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Option) */ {
  public:
-  inline Option() : Option(nullptr) {};
+  inline Option() : Option(nullptr) {}
   virtual ~Option();
 
   Option(const Option& from);
diff --git a/src/google/protobuf/util/internal/json_stream_parser.cc b/src/google/protobuf/util/internal/json_stream_parser.cc
index b94e3c2..8cb22c7 100644
--- a/src/google/protobuf/util/internal/json_stream_parser.cc
+++ b/src/google/protobuf/util/internal/json_stream_parser.cc
@@ -82,8 +82,8 @@
 
 // Indicates a character may not be part of an unquoted key.
 inline bool IsKeySeparator(char c) {
-  return (ascii_isspace(c) || c == '"' || c == '\'' || c == '{' || c == '}' ||
-          c == '[' || c == ']' || c == ':' || c == ',');
+  return (ascii_isspace(c) || c == '"' || c == '\'' || c == '{' ||
+          c == '}' || c == '[' || c == ']' || c == ':' || c == ',');
 }
 
 inline void ReplaceInvalidCodePoints(StringPiece str,
diff --git a/src/google/protobuf/util/internal/proto_writer.cc b/src/google/protobuf/util/internal/proto_writer.cc
index ea95932..de93085 100644
--- a/src/google/protobuf/util/internal/proto_writer.cc
+++ b/src/google/protobuf/util/internal/proto_writer.cc
@@ -406,7 +406,9 @@
         now->parent()->parent_field_ != now->parent_field_) {
       std::string name = now->parent_field_->name();
       int i = 0;
-      while (i < name.size() && (ascii_isalnum(name[i]) || name[i] == '_')) ++i;
+      while (i < name.size() &&
+             (ascii_isalnum(name[i]) || name[i] == '_'))
+        ++i;
       if (i > 0 && i == name.size()) {  // safe field name
         if (loc.empty()) {
           loc = name;
diff --git a/src/google/protobuf/util/internal/utility.cc b/src/google/protobuf/util/internal/utility.cc
index e3cdbcb..84682fa 100644
--- a/src/google/protobuf/util/internal/utility.cc
+++ b/src/google/protobuf/util/internal/utility.cc
@@ -270,7 +270,8 @@
       // 1) following a lowercase:   "...aB..."
       // 2) followed by a lowercase: "...ABc..."
       if (!result.empty() && is_cap &&
-          (!was_cap || (i + 1 < input.size() && ascii_islower(input[i + 1])))) {
+          (!was_cap ||
+           (i + 1 < input.size() && ascii_islower(input[i + 1])))) {
         first_word = false;
         result.push_back(input[i]);
       } else {
@@ -310,9 +311,9 @@
       //    (e.g. "GoogleLAB" => "google_lab")
       // 4) Followed by a lowercase: "...ABc..." => "...a_bc..."
       //    (e.g. "GBike" => "g_bike")
-      if (was_not_underscore &&               //            case 1 out
-          (was_not_cap ||                     // case 2 in, case 3 out
-           (i + 1 < input.size() &&           //            case 3 out
+      if (was_not_underscore &&                     //            case 1 out
+          (was_not_cap ||                           // case 2 in, case 3 out
+           (i + 1 < input.size() &&                 //            case 3 out
             ascii_islower(input[i + 1])))) {  // case 4 in
         // We add an underscore for case 2 and case 4.
         result.push_back('_');
diff --git a/src/google/protobuf/wrappers.pb.h b/src/google/protobuf/wrappers.pb.h
index d6ee3fc..14c6480 100644
--- a/src/google/protobuf/wrappers.pb.h
+++ b/src/google/protobuf/wrappers.pb.h
@@ -101,7 +101,7 @@
 class PROTOBUF_EXPORT DoubleValue PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.DoubleValue) */ {
  public:
-  inline DoubleValue() : DoubleValue(nullptr) {};
+  inline DoubleValue() : DoubleValue(nullptr) {}
   virtual ~DoubleValue();
 
   DoubleValue(const DoubleValue& from);
@@ -238,7 +238,7 @@
 class PROTOBUF_EXPORT FloatValue PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.FloatValue) */ {
  public:
-  inline FloatValue() : FloatValue(nullptr) {};
+  inline FloatValue() : FloatValue(nullptr) {}
   virtual ~FloatValue();
 
   FloatValue(const FloatValue& from);
@@ -375,7 +375,7 @@
 class PROTOBUF_EXPORT Int64Value PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Int64Value) */ {
  public:
-  inline Int64Value() : Int64Value(nullptr) {};
+  inline Int64Value() : Int64Value(nullptr) {}
   virtual ~Int64Value();
 
   Int64Value(const Int64Value& from);
@@ -512,7 +512,7 @@
 class PROTOBUF_EXPORT UInt64Value PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.UInt64Value) */ {
  public:
-  inline UInt64Value() : UInt64Value(nullptr) {};
+  inline UInt64Value() : UInt64Value(nullptr) {}
   virtual ~UInt64Value();
 
   UInt64Value(const UInt64Value& from);
@@ -649,7 +649,7 @@
 class PROTOBUF_EXPORT Int32Value PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.Int32Value) */ {
  public:
-  inline Int32Value() : Int32Value(nullptr) {};
+  inline Int32Value() : Int32Value(nullptr) {}
   virtual ~Int32Value();
 
   Int32Value(const Int32Value& from);
@@ -786,7 +786,7 @@
 class PROTOBUF_EXPORT UInt32Value PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.UInt32Value) */ {
  public:
-  inline UInt32Value() : UInt32Value(nullptr) {};
+  inline UInt32Value() : UInt32Value(nullptr) {}
   virtual ~UInt32Value();
 
   UInt32Value(const UInt32Value& from);
@@ -923,7 +923,7 @@
 class PROTOBUF_EXPORT BoolValue PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.BoolValue) */ {
  public:
-  inline BoolValue() : BoolValue(nullptr) {};
+  inline BoolValue() : BoolValue(nullptr) {}
   virtual ~BoolValue();
 
   BoolValue(const BoolValue& from);
@@ -1060,7 +1060,7 @@
 class PROTOBUF_EXPORT StringValue PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.StringValue) */ {
  public:
-  inline StringValue() : StringValue(nullptr) {};
+  inline StringValue() : StringValue(nullptr) {}
   virtual ~StringValue();
 
   StringValue(const StringValue& from);
@@ -1204,7 +1204,7 @@
 class PROTOBUF_EXPORT BytesValue PROTOBUF_FINAL :
     public ::PROTOBUF_NAMESPACE_ID::Message /* @@protoc_insertion_point(class_definition:google.protobuf.BytesValue) */ {
  public:
-  inline BytesValue() : BytesValue(nullptr) {};
+  inline BytesValue() : BytesValue(nullptr) {}
   virtual ~BytesValue();
 
   BytesValue(const BytesValue& from);
diff --git a/tests.sh b/tests.sh
index 0a0e798..ca998e1 100755
--- a/tests.sh
+++ b/tests.sh
@@ -305,8 +305,6 @@
 }
 
 build_objectivec_cocoapods_integration() {
-  # Update pod to the latest version.
-  gem install cocoapods --no_document
   objectivec/Tests/CocoaPods/run_tests.sh
 }
 
@@ -457,48 +455,16 @@
   cd conformance && make test_nodejs && cd ..
 }
 
-generate_php_test_proto() {
-  internal_build_cpp
-  pushd php/tests
-  # Generate test file
-  rm -rf generated
-  mkdir generated
-  ../../src/protoc --php_out=generated         \
-    -I../../src -I.                            \
-    proto/empty/echo.proto                     \
-    proto/test.proto                           \
-    proto/test_include.proto                   \
-    proto/test_no_namespace.proto              \
-    proto/test_prefix.proto                    \
-    proto/test_php_namespace.proto             \
-    proto/test_empty_php_namespace.proto       \
-    proto/test_reserved_enum_lower.proto       \
-    proto/test_reserved_enum_upper.proto       \
-    proto/test_reserved_enum_value_lower.proto \
-    proto/test_reserved_enum_value_upper.proto \
-    proto/test_reserved_message_lower.proto    \
-    proto/test_reserved_message_upper.proto    \
-    proto/test_service.proto                   \
-    proto/test_service_namespace.proto         \
-    proto/test_wrapper_type_setters.proto      \
-    proto/test_descriptors.proto
-  pushd ../../src
-  ./protoc --php_out=../php/tests/generated -I../php/tests -I. \
-    ../php/tests/proto/test_import_descriptor_proto.proto
-  popd
-  popd
-}
-
 use_php() {
   VERSION=$1
   export PATH=/usr/local/php-${VERSION}/bin:$PATH
-  generate_php_test_proto
+  internal_build_cpp
 }
 
 use_php_zts() {
   VERSION=$1
   export PATH=/usr/local/php-${VERSION}-zts/bin:$PATH
-  generate_php_test_proto
+  internal_build_cpp
 }
 
 build_php5.5() {
@@ -507,11 +473,9 @@
   pushd php
   rm -rf vendor
   composer update
-  ./vendor/bin/phpunit
+  composer test
   popd
-  pushd conformance
-  make test_php
-  popd
+  (cd conformance && make test_php)
 }
 
 build_php5.5_c() {
@@ -534,6 +498,7 @@
   rm -rf vendor
   composer update
   tests/compile_extension.sh
+  tests/generate_protos.sh
   php -dextension=./ext/google/protobuf/modules/protobuf.so ./vendor/bin/phpunit
   popd
 }
@@ -557,11 +522,9 @@
   pushd php
   rm -rf vendor
   composer update
-  ./vendor/bin/phpunit
+  composer test
   popd
-  pushd conformance
-  make test_php
-  popd
+  (cd conformance && make test_php)
 }
 
 build_php5.6_c() {
@@ -584,6 +547,7 @@
   rm -rf vendor
   composer update
   tests/compile_extension.sh
+  tests/generate_protos.sh
   php -dextension=./ext/google/protobuf/modules/protobuf.so ./vendor/bin/phpunit
   popd
 }
@@ -603,18 +567,13 @@
 }
 
 build_php5.6_mac() {
-  generate_php_test_proto
+  internal_build_cpp
   # Install PHP
   curl -s https://php-osx.liip.ch/install.sh | bash -s 5.6
   PHP_FOLDER=`find /usr/local -type d -name "php5-5.6*"`  # The folder name may change upon time
   test ! -z "$PHP_FOLDER"
   export PATH="$PHP_FOLDER/bin:$PATH"
 
-  # Install phpunit
-  curl https://phar.phpunit.de/phpunit-5.6.8.phar -L -o phpunit.phar
-  chmod +x phpunit.phar
-  sudo mv phpunit.phar /usr/local/bin/phpunit
-
   # Install valgrind
   echo "#! /bin/bash" > valgrind
   chmod ug+x valgrind
@@ -630,7 +589,7 @@
   pushd php
   rm -rf vendor
   composer update
-  ./vendor/bin/phpunit
+  composer test
   popd
   (cd conformance && make test_php)
 }
@@ -655,6 +614,7 @@
   rm -rf vendor
   composer update
   tests/compile_extension.sh
+  tests/generate_protos.sh
   php -dextension=./ext/google/protobuf/modules/protobuf.so ./vendor/bin/phpunit
   popd
 }
@@ -674,18 +634,13 @@
 }
 
 build_php7.0_mac() {
-  generate_php_test_proto
+  internal_build_cpp
   # Install PHP
   curl -s https://php-osx.liip.ch/install.sh | bash -s 7.0
   PHP_FOLDER=`find /usr/local -type d -name "php5-7.0*"`  # The folder name may change upon time
   test ! -z "$PHP_FOLDER"
   export PATH="$PHP_FOLDER/bin:$PATH"
 
-  # Install phpunit
-  curl https://phar.phpunit.de/phpunit-5.6.0.phar -L -o phpunit.phar
-  chmod +x phpunit.phar
-  sudo mv phpunit.phar /usr/local/bin/phpunit
-
   # Install valgrind
   echo "#! /bin/bash" > valgrind
   chmod ug+x valgrind
@@ -697,7 +652,7 @@
 }
 
 build_php7.3_mac() {
-  generate_php_test_proto
+  internal_build_cpp
   # Install PHP
   # We can't test PHP 7.4 with these binaries yet:
   #   https://github.com/liip/php-osx/issues/276
@@ -706,11 +661,6 @@
   test ! -z "$PHP_FOLDER"
   export PATH="$PHP_FOLDER/bin:$PATH"
 
-  # Install phpunit
-  curl https://phar.phpunit.de/phpunit-8.phar -L -o phpunit.phar
-  chmod +x phpunit.phar
-  sudo mv phpunit.phar /usr/local/bin/phpunit
-
   # Install valgrind
   echo "#! /bin/bash" > valgrind
   chmod ug+x valgrind
@@ -736,7 +686,7 @@
   pushd php
   rm -rf vendor
   composer update
-  ./vendor/bin/phpunit
+  composer test
   popd
   (cd conformance && make test_php)
 }
@@ -761,6 +711,7 @@
   rm -rf vendor
   composer update
   tests/compile_extension.sh
+  tests/generate_protos.sh
   php -dextension=./ext/google/protobuf/modules/protobuf.so ./vendor/bin/phpunit
   popd
 }
@@ -784,7 +735,7 @@
   pushd php
   rm -rf vendor
   composer update
-  ./vendor/bin/phpunit
+  composer test
   popd
   (cd conformance && make test_php)
 }
@@ -810,6 +761,7 @@
   rm -rf vendor
   composer update
   tests/compile_extension.sh
+  tests/generate_protos.sh
   php -dextension=./ext/google/protobuf/modules/protobuf.so ./vendor/bin/phpunit
   popd
   (cd php/ext/google/protobuf && phpize --clean)