gmock_cook_book: Document `DoAll`'s return type requirement
The requirement is vaguely documented by "Only the return value of the last action in the sequence will be used.".
However, this can be misleading, as users could potentially expect default-constructed values to be returned in absence of a matching return type.
PiperOrigin-RevId: 570450839
Change-Id: Ibd98a6e6b2aaf2a8cfc15ed6aeab442526eab98e
diff --git a/docs/gmock_cook_book.md b/docs/gmock_cook_book.md
index da10918..5e9b664 100644
--- a/docs/gmock_cook_book.md
+++ b/docs/gmock_cook_book.md
@@ -1927,6 +1927,12 @@
action_n));
```
+The return value of the last action **must** match the return type of the mocked
+method. In the example above, `action_n` could be `Return(true)`, or a lambda
+that returns a `bool`, but not `SaveArg`, which returns `void`. Otherwise the
+signature of `DoAll` would not match the signature expected by `WillOnce`, which
+is the signature of the mocked method, and it wouldn't compile.
+
### Verifying Complex Arguments {#SaveArgVerify}
If you want to verify that a method is called with a particular argument but the
