absl/base/nullability_test.cc

// Copyright 2023 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "absl/base/nullability.h"

#include <cassert>
#include <memory>
#include <utility>

#include "gtest/gtest.h"
#include "absl/base/attributes.h"

namespace {
using ::absl::Nonnull;
using ::absl::NullabilityUnknown;
using ::absl::Nullable;

void funcWithNonnullArg(Nonnull<int*> /*arg*/) {}
template <typename T>
void funcWithDeducedNonnullArg(Nonnull<T*> /*arg*/) {}

TEST(NonnullTest, NonnullArgument) {
  int var = 0;
  funcWithNonnullArg(&var);
  funcWithDeducedNonnullArg(&var);
}

Nonnull<int*> funcWithNonnullReturn() {
  static int var = 0;
  return &var;
}

TEST(NonnullTest, NonnullReturn) {
  auto var = funcWithNonnullReturn();
  (void)var;
}

TEST(PassThroughTest, PassesThroughRawPointerToInt) {
  EXPECT_TRUE((std::is_same<Nonnull<int*>, int*>::value));
  EXPECT_TRUE((std::is_same<Nullable<int*>, int*>::value));
  EXPECT_TRUE((std::is_same<NullabilityUnknown<int*>, int*>::value));
}

TEST(PassThroughTest, PassesThroughRawPointerToVoid) {
  EXPECT_TRUE((std::is_same<Nonnull<void*>, void*>::value));
  EXPECT_TRUE((std::is_same<Nullable<void*>, void*>::value));
  EXPECT_TRUE((std::is_same<NullabilityUnknown<void*>, void*>::value));
}

TEST(PassThroughTest, PassesThroughUniquePointerToInt) {
  using T = std::unique_ptr<int>;
  EXPECT_TRUE((std::is_same<Nonnull<T>, T>::value));
  EXPECT_TRUE((std::is_same<Nullable<T>, T>::value));
  EXPECT_TRUE((std::is_same<NullabilityUnknown<T>, T>::value));
}

TEST(PassThroughTest, PassesThroughSharedPointerToInt) {
  using T = std::shared_ptr<int>;
  EXPECT_TRUE((std::is_same<Nonnull<T>, T>::value));
  EXPECT_TRUE((std::is_same<Nullable<T>, T>::value));
  EXPECT_TRUE((std::is_same<NullabilityUnknown<T>, T>::value));
}

TEST(PassThroughTest, PassesThroughSharedPointerToVoid) {
  using T = std::shared_ptr<void>;
  EXPECT_TRUE((std::is_same<Nonnull<T>, T>::value));
  EXPECT_TRUE((std::is_same<Nullable<T>, T>::value));
  EXPECT_TRUE((std::is_same<NullabilityUnknown<T>, T>::value));
}

TEST(PassThroughTest, PassesThroughPointerToMemberObject) {
  using T = decltype(&std::pair<int, int>::first);
  EXPECT_TRUE((std::is_same<Nonnull<T>, T>::value));
  EXPECT_TRUE((std::is_same<Nullable<T>, T>::value));
  EXPECT_TRUE((std::is_same<NullabilityUnknown<T>, T>::value));
}

TEST(PassThroughTest, PassesThroughPointerToMemberFunction) {
  using T = decltype(&std::unique_ptr<int>::reset);
  EXPECT_TRUE((std::is_same<Nonnull<T>, T>::value));
  EXPECT_TRUE((std::is_same<Nullable<T>, T>::value));
  EXPECT_TRUE((std::is_same<NullabilityUnknown<T>, T>::value));
}

}  // namespace

// Nullable ADL lookup test
namespace util {
// Helper for NullableAdlTest.  Returns true, denoting that argument-dependent
// lookup found this implementation of DidAdlWin.  Must be in namespace
// util itself, not a nested anonymous namespace.
template <typename T>
bool DidAdlWin(T*) {
  return true;
}

// Because this type is defined in namespace util, an unqualified call to
// DidAdlWin with a pointer to MakeAdlWin will find the above implementation.
struct MakeAdlWin {};
}  // namespace util

namespace {
// Returns false, denoting that ADL did not inspect namespace util.  If it
// had, the better match (T*) above would have won out over the (...) here.
bool DidAdlWin(...) { return false; }

TEST(NullableAdlTest, NullableAddsNothingToArgumentDependentLookup) {
  // Treatment: util::Nullable<int*> contributes nothing to ADL because
  // int* itself doesn't.
  EXPECT_FALSE(DidAdlWin((int*)nullptr));
  EXPECT_FALSE(DidAdlWin((Nullable<int*>)nullptr));

  // Control: Argument-dependent lookup does find the implementation in
  // namespace util when the underlying pointee type resides there.
  EXPECT_TRUE(DidAdlWin((util::MakeAdlWin*)nullptr));
  EXPECT_TRUE(DidAdlWin((Nullable<util::MakeAdlWin*>)nullptr));
}
}  // namespace