path: root/absl/meta/type_traits_test.cc

// Copyright 2017 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
//
//      http://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/meta/type_traits.h"

#include <cstdint>
#include <string>
#include <type_traits>
#include <utility>
#include <vector>

#include "gtest/gtest.h"

namespace {

using ::testing::StaticAssertTypeEq;

template <class T, class U>
struct simple_pair {
  T first;
  U second;
};

struct Dummy {};

struct ReturnType {};
struct ConvertibleToReturnType {
  operator ReturnType() const;  // NOLINT
};

// Unique types used as parameter types for testing the detection idiom.
struct StructA {};
struct StructB {};
struct StructC {};

struct TypeWithBarFunction {
  template <class T,
            absl::enable_if_t<std::is_same<T&&, StructA&>::value, int> = 0>
  ReturnType bar(T&&, const StructB&, StructC&&) &&;  // NOLINT
};

struct TypeWithBarFunctionAndConvertibleReturnType {
  template <class T,
            absl::enable_if_t<std::is_same<T&&, StructA&>::value, int> = 0>
  ConvertibleToReturnType bar(T&&, const StructB&, StructC&&) &&;  // NOLINT
};

template <class Class, class... Ts>
using BarIsCallableImpl =
    decltype(std::declval<Class>().bar(std::declval<Ts>()...));

template <class Class, class... T>
using BarIsCallable =
    absl::type_traits_internal::is_detected<BarIsCallableImpl, Class, T...>;

template <class Class, class... T>
using BarIsCallableConv = absl::type_traits_internal::is_detected_convertible<
    ReturnType, BarIsCallableImpl, Class, T...>;

// NOTE: Test of detail type_traits_internal::is_detected.
TEST(IsDetectedTest, BasicUsage) {
  EXPECT_TRUE((BarIsCallable<TypeWithBarFunction, StructA&, const StructB&,
                             StructC>::value));
  EXPECT_TRUE(
      (BarIsCallable<TypeWithBarFunction, StructA&, StructB&, StructC>::value));
  EXPECT_TRUE(
      (BarIsCallable<TypeWithBarFunction, StructA&, StructB, StructC>::value));

  EXPECT_FALSE((BarIsCallable<int, StructA&, const StructB&, StructC>::value));
  EXPECT_FALSE((BarIsCallable<TypeWithBarFunction&, StructA&, const StructB&,
                              StructC>::value));
  EXPECT_FALSE((BarIsCallable<TypeWithBarFunction, StructA, const StructB&,
                              StructC>::value));
}

// NOTE: Test of detail type_traits_internal::is_detected_convertible.
TEST(IsDetectedConvertibleTest, BasicUsage) {
  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunction, StructA&, const StructB&,
                                 StructC>::value));
  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunction, StructA&, StructB&,
                                 StructC>::value));
  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunction, StructA&, StructB,
                                 StructC>::value));
  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
                                 StructA&, const StructB&, StructC>::value));
  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
                                 StructA&, StructB&, StructC>::value));
  EXPECT_TRUE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
                                 StructA&, StructB, StructC>::value));

  EXPECT_FALSE(
      (BarIsCallableConv<int, StructA&, const StructB&, StructC>::value));
  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunction&, StructA&,
                                  const StructB&, StructC>::value));
  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunction, StructA, const StructB&,
                                  StructC>::value));
  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType&,
                                  StructA&, const StructB&, StructC>::value));
  EXPECT_FALSE((BarIsCallableConv<TypeWithBarFunctionAndConvertibleReturnType,
                                  StructA, const StructB&, StructC>::value));
}

TEST(VoidTTest, BasicUsage) {
  StaticAssertTypeEq<void, absl::void_t<Dummy>>();
  StaticAssertTypeEq<void, absl::void_t<Dummy, Dummy, Dummy>>();
}

TEST(ConjunctionTest, BasicBooleanLogic) {
  EXPECT_TRUE(absl::conjunction<>::value);
  EXPECT_TRUE(absl::conjunction<std::true_type>::value);
  EXPECT_TRUE((absl::conjunction<std::true_type, std::true_type>::value));
  EXPECT_FALSE((absl::conjunction<std::true_type, std::false_type>::value));
  EXPECT_FALSE((absl::conjunction<std::false_type, std::true_type>::value));
  EXPECT_FALSE((absl::conjunction<std::false_type, std::false_type>::value));
}

struct MyTrueType {
  static constexpr bool value = true;
};

struct MyFalseType {
  static constexpr bool value = false;
};

TEST(ConjunctionTest, ShortCircuiting) {
  EXPECT_FALSE(
      (absl::conjunction<std::true_type, std::false_type, Dummy>::value));
  EXPECT_TRUE((std::is_base_of<MyFalseType,
                               absl::conjunction<std::true_type, MyFalseType,
                                                 std::false_type>>::value));
  EXPECT_TRUE(
      (std::is_base_of<MyTrueType,
                       absl::conjunction<std::true_type, MyTrueType>>::value));
}

TEST(DisjunctionTest, BasicBooleanLogic) {
  EXPECT_FALSE(absl::disjunction<>::value);
  EXPECT_FALSE(absl::disjunction<std::false_type>::value);
  EXPECT_TRUE((absl::disjunction<std::true_type, std::true_type>::value));
  EXPECT_TRUE((absl::disjunction<std::true_type, std::false_type>::value));
  EXPECT_TRUE((absl::disjunction<std::false_type, std::true_type>::value));
  EXPECT_FALSE((absl::disjunction<std::false_type, std::false_type>::value));
}

TEST(DisjunctionTest, ShortCircuiting) {
  EXPECT_TRUE(
      (absl::disjunction<std::false_type, std::true_type, Dummy>::value));
  EXPECT_TRUE((
      std::is_base_of<MyTrueType, absl::disjunction<std::false_type, MyTrueType,
                                                    std::true_type>>::value));
  EXPECT_TRUE((
      std::is_base_of<MyFalseType,
                      absl::disjunction<std::false_type, MyFalseType>>::value));
}

TEST(NegationTest, BasicBooleanLogic) {
  EXPECT_FALSE(absl::negation<std::true_type>::value);
  EXPECT_FALSE(absl::negation<MyTrueType>::value);
  EXPECT_TRUE(absl::negation<std::false_type>::value);
  EXPECT_TRUE(absl::negation<MyFalseType>::value);
}

// all member functions are trivial
class Trivial {
  int n_;
};

struct TrivialDestructor {
  ~TrivialDestructor() = default;
};

struct NontrivialDestructor {
  ~NontrivialDestructor() {}
};

struct DeletedDestructor {
  ~DeletedDestructor() = delete;
};

class TrivialDefaultCtor {
 public:
  TrivialDefaultCtor() = default;
  explicit TrivialDefaultCtor(int n) : n_(n) {}

 private:
  int n_;
};

class NontrivialDefaultCtor {
 public:
  NontrivialDefaultCtor() : n_(1) {}

 private:
  int n_;
};

class DeletedDefaultCtor {
 public:
  DeletedDefaultCtor() = delete;
  explicit DeletedDefaultCtor(int n) : n_(n) {}

 private:
  int n_;
};

class TrivialCopyCtor {
 public:
  explicit TrivialCopyCtor(int n) : n_(n) {}
  TrivialCopyCtor(const TrivialCopyCtor&) = default;
  TrivialCopyCtor& operator=(const TrivialCopyCtor& t) {
    n_ = t.n_;
    return *this;
  }

 private:
  int n_;
};

class NontrivialCopyCtor {
 public:
  explicit NontrivialCopyCtor(int n) : n_(n) {}
  NontrivialCopyCtor(const NontrivialCopyCtor& t) : n_(t.n_) {}
  NontrivialCopyCtor& operator=(const NontrivialCopyCtor&) = default;

 private:
  int n_;
};

class DeletedCopyCtor {
 public:
  explicit DeletedCopyCtor(int n) : n_(n) {}
  DeletedCopyCtor(const DeletedCopyCtor&) = delete;
  DeletedCopyCtor& operator=(const DeletedCopyCtor&) = default;

 private:
  int n_;
};

class TrivialCopyAssign {
 public:
  explicit TrivialCopyAssign(int n) : n_(n) {}
  TrivialCopyAssign(const TrivialCopyAssign& t) : n_(t.n_) {}
  TrivialCopyAssign& operator=(const TrivialCopyAssign& t) = default;
  ~TrivialCopyAssign() {}  // can have nontrivial destructor
 private:
  int n_;
};

class NontrivialCopyAssign {
 public:
  explicit NontrivialCopyAssign(int n) : n_(n) {}
  NontrivialCopyAssign(const NontrivialCopyAssign&) = default;
  NontrivialCopyAssign& operator=(const NontrivialCopyAssign& t) {
    n_ = t.n_;
    return *this;
  }

 private:
  int n_;
};

class DeletedCopyAssign {
 public:
  explicit DeletedCopyAssign(int n) : n_(n) {}
  DeletedCopyAssign(const DeletedCopyAssign&) = default;
  DeletedCopyAssign& operator=(const DeletedCopyAssign&) = delete;

 private:
  int n_;
};

struct NonCopyable {
  NonCopyable() = default;
  NonCopyable(const NonCopyable&) = delete;
  NonCopyable& operator=(const NonCopyable&) = delete;
};

class Base {
 public:
  virtual ~Base() {}
};

// In GCC/Clang, std::is_trivially_constructible requires that the destructor is
// trivial. However, MSVC doesn't require that. This results in different
// behavior when checking is_trivially_constructible on any type with
// nontrivial destructor. Since absl::is_trivially_default_constructible and
// absl::is_trivially_copy_constructible both follows Clang/GCC's interpretation
// and check is_trivially_destructible, it results in inconsistency with
// std::is_trivially_xxx_constructible on MSVC. This macro is used to work
// around this issue in test. In practice, a trivially constructible type
// should also be trivially destructible.
// GCC bug 51452: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51452
// LWG issue 2116: http://cplusplus.github.io/LWG/lwg-active.html#2116
#ifndef _MSC_VER
#define ABSL_TRIVIALLY_CONSTRUCTIBLE_VERIFY_TRIVIALLY_DESTRUCTIBLE 1
#endif

// Old versions of libc++, around Clang 3.5 to 3.6, consider deleted destructors
// as also being trivial. With the resolution of CWG 1928 and CWG 1734, this
// is no longer considered true and has thus been amended.
// Compiler Explorer: https://godbolt.org/g/zT59ZL
// CWG issue 1734: http://open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#1734
// CWG issue 1928: http://open-std.org/JTC1/SC22/WG21/docs/cwg_closed.html#1928
#if !defined(_LIBCPP_VERSION) || _LIBCPP_VERSION >= 3700
#define ABSL_TRIVIALLY_DESTRUCTIBLE_CONSIDER_DELETED_DESTRUCTOR_NOT_TRIVIAL 1
#endif

// As of the moment, GCC versions >5.1 have a problem compiling for
// std::is_trivially_default_constructible<NontrivialDestructor[10]>, where
// NontrivialDestructor is a struct with a custom nontrivial destructor. Note
// that this problem only occurs for arrays of a known size, so something like
// std::is_trivially_default_constructible<NontrivialDestructor[]> does not
// have any problems.
// Compiler Explorer: https://godbolt.org/g/dXRbdK
// GCC bug 83689: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83689
#if defined(__clang__) || defined(_MSC_VER) || \
    (defined(__GNUC__) && __GNUC__ < 5)
#define ABSL_GCC_BUG_TRIVIALLY_CONSTRUCTIBLE_ON_ARRAY_OF_NONTRIVIAL 1
#endif

TEST(TypeTraitsTest, TestTrivialDestructor) {
  // Verify that arithmetic types and pointers have trivial destructors.
  EXPECT_TRUE(absl::is_trivially_destructible<bool>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<char>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<unsigned char>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<signed char>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<wchar_t>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<int>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<unsigned int>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<int16_t>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<uint16_t>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<int64_t>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<uint64_t>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<float>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<double>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<long double>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<std::string*>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<Trivial*>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<const std::string*>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<const Trivial*>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<std::string**>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<Trivial**>::value);

  // classes with destructors
  EXPECT_TRUE(absl::is_trivially_destructible<Trivial>::value);
  EXPECT_TRUE(absl::is_trivially_destructible<TrivialDestructor>::value);

  // Verify that types with a nontrivial or deleted destructor
  // are marked as such.
  EXPECT_FALSE(absl::is_trivially_destructible<NontrivialDestructor>::value);
#ifdef ABSL_TRIVIALLY_DESTRUCTIBLE_CONSIDER_DELETED_DESTRUCTOR_NOT_TRIVIAL
  EXPECT_FALSE(absl::is_trivially_destructible<DeletedDestructor>::value);
#endif

  // simple_pair of such types is trivial
  EXPECT_TRUE((absl::is_trivially_destructible<simple_pair<int, int>>::value));
  EXPECT_TRUE((absl::is_trivially_destructible<
               simple_pair<Trivial, TrivialDestructor>>::value));

  // Verify that types without trivial destructors are correctly marked as such.
  EXPECT_FALSE(absl::is_trivially_destructible<std::string>::value);
  EXPECT_FALSE(absl::is_trivially_destructible<std::vector<int>>::value);

  // Verify that simple_pairs of types without trivial destructors
  // are not marked as trivial.
  EXPECT_FALSE((absl::is_trivially_destructible<
                simple_pair<int, std::string>>::value));
  EXPECT_FALSE((absl::is_trivially_destructible<
                simple_pair<std::string, int>>::value));

  // array of such types is trivial
  using int10 = int[10];
  EXPECT_TRUE(absl::is_trivially_destructible<int10>::value);
  using Trivial10 = Trivial[10];
  EXPECT_TRUE(absl::is_trivially_destructible<Trivial10>::value);
  using TrivialDestructor10 = TrivialDestructor[10];
  EXPECT_TRUE(absl::is_trivially_destructible<TrivialDestructor10>::value);

  // Conversely, the opposite also holds.
  using NontrivialDestructor10 = NontrivialDestructor[10];
  EXPECT_FALSE(absl::is_trivially_destructible<NontrivialDestructor10>::value);
}

TEST(TypeTraitsTest, TestTrivialDefaultCtor) {
  // arithmetic types and pointers have trivial default constructors.
  EXPECT_TRUE(absl::is_trivially_default_constructible<bool>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<char>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<unsigned char>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<signed char>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<wchar_t>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<int>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<unsigned int>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<int16_t>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<uint16_t>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<int64_t>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<uint64_t>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<float>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<double>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<long double>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<std::string*>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<Trivial*>::value);
  EXPECT_TRUE(
      absl::is_trivially_default_constructible<const std::string*>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<const Trivial*>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<std::string**>::value);
  EXPECT_TRUE(absl::is_trivially_default_constructible<Trivial**>::value);

  // types with compiler generated default ctors
  EXPECT_TRUE(absl::is_trivially_default_constructible<Trivial>::value);
  EXPECT_TRUE(
      absl::is_trivially_default_constructible<TrivialDefaultCtor>::value);

  // Verify that types without them are not.
  EXPECT_FALSE(
      absl::is_trivially_default_constructible<NontrivialDefaultCtor>::value);
  EXPECT_FALSE(
      absl::is_trivially_default_constructible<DeletedDefaultCtor>::value);

#ifdef ABSL_TRIVIALLY_CONSTRUCTIBLE_VERIFY_TRIVIALLY_DESTRUCTIBLE
  // types with nontrivial destructor are nontrivial
  EXPECT_FALSE(
      absl::is_trivially_default_constructible<NontrivialDestructor>::value);
#endif

  // types with vtables
  EXPECT_FALSE(absl::is_trivially_default_constructible<Base>::value);

  // Verify that simple_pair has trivial constructors where applicable.
  EXPECT_TRUE((absl::is_trivially_default_constructible<
               simple_pair<int, char*>>::value));
  EXPECT_TRUE((absl::is_trivially_default_constructible<
               simple_pair<int, Trivial>>::value));
  EXPECT_TRUE((absl::is_trivially_default_constructible<
               simple_pair<int, TrivialDefaultCtor>>::value));

  // Verify that types without trivial constructors are
  // correctly marked as such.
  EXPECT_FALSE(absl::is_trivially_default_constructible<std::string>::value);
  EXPECT_FALSE(
      absl::is_trivially_default_constructible<std::vector<int>>::value);

  // Verify that simple_pairs of types without trivial constructors
  // are not marked as trivial.
  EXPECT_FALSE((absl::is_trivially_default_constructible<
                simple_pair<int, std::string>>::value));
  EXPECT_FALSE((absl::is_trivially_default_constructible<
                simple_pair<std::string, int>>::value));

  // Verify that arrays of such types are trivially default constructible
  using int10 = int[10];
  EXPECT_TRUE(absl::is_trivially_default_constructible<int10>::value);
  using Trivial10 = Trivial[10];
  EXPECT_TRUE(absl::is_trivially_default_constructible<Trivial10>::value);
  using TrivialDefaultCtor10 = TrivialDefaultCtor[10];
  EXPECT_TRUE(
      absl::is_trivially_default_constructible<TrivialDefaultCtor10>::value);

  // Conversely, the opposite also holds.
#ifdef ABSL_GCC_BUG_TRIVIALLY_CONSTRUCTIBLE_ON_ARRAY_OF_NONTRIVIAL
  using NontrivialDefaultCtor10 = NontrivialDefaultCtor[10];
  EXPECT_FALSE(
      absl::is_trivially_default_constructible<NontrivialDefaultCtor10>::value);
#endif
}

TEST(TypeTraitsTest, TestTrivialCopyCtor) {
  // Verify that arithmetic types and pointers have trivial copy
  // constructors.
  EXPECT_TRUE(absl::is_trivially_copy_constructible<bool>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<char>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<unsigned char>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<signed char>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<wchar_t>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<int>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<unsigned int>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<int16_t>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<uint16_t>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<int64_t>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<uint64_t>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<float>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<double>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<long double>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<std::string*>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<Trivial*>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<const std::string*>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<const Trivial*>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<std::string**>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<Trivial**>::value);

  // types with compiler generated copy ctors
  EXPECT_TRUE(absl::is_trivially_copy_constructible<Trivial>::value);
  EXPECT_TRUE(absl::is_trivially_copy_constructible<TrivialCopyCtor>::value);

  // Verify that types without them (i.e. nontrivial or deleted) are not.
  EXPECT_FALSE(
      absl::is_trivially_copy_constructible<NontrivialCopyCtor>::value);
  EXPECT_FALSE(absl::is_trivially_copy_constructible<DeletedCopyCtor>::value);
  EXPECT_FALSE(
      absl::is_trivially_copy_constructible<NonCopyable>::value);

#ifdef ABSL_TRIVIALLY_CONSTRUCTIBLE_VERIFY_TRIVIALLY_DESTRUCTIBLE
  // type with nontrivial destructor are nontrivial copy construbtible
  EXPECT_FALSE(
      absl::is_trivially_copy_constructible<NontrivialDestructor>::value);
#endif

  // types with vtables
  EXPECT_FALSE(absl::is_trivially_copy_constructible<Base>::value);

  // Verify that simple_pair of such types is trivially copy constructible
  EXPECT_TRUE(
      (absl::is_trivially_copy_constructible<simple_pair<int, char*>>::value));
  EXPECT_TRUE((
      absl::is_trivially_copy_constructible<simple_pair<int, Trivial>>::value));
  EXPECT_TRUE((absl::is_trivially_copy_constructible<
               simple_pair<int, TrivialCopyCtor>>::value));

  // Verify that types without trivial copy constructors are
  // correctly marked as such.
  EXPECT_FALSE(absl::is_trivially_copy_constructible<std::string>::value);
  EXPECT_FALSE(absl::is_trivially_copy_constructible<std::vector<int>>::value);

  // Verify that simple_pairs of types without trivial copy constructors
  // are not marked as trivial.
  EXPECT_FALSE((absl::is_trivially_copy_constructible<
                simple_pair<int, std::string>>::value));
  EXPECT_FALSE((absl::is_trivially_copy_constructible<
                simple_pair<std::string, int>>::value));

  // Verify that arrays are not
  using int10 = int[10];
  EXPECT_FALSE(absl::is_trivially_copy_constructible<int10>::value);
}

TEST(TypeTraitsTest, TestTrivialCopyAssign) {
  // Verify that arithmetic types and pointers have trivial copy
  // assignment operators.
  EXPECT_TRUE(absl::is_trivially_copy_assignable<bool>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<char>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<unsigned char>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<signed char>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<wchar_t>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<int>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<unsigned int>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<int16_t>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<uint16_t>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<int64_t>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<uint64_t>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<float>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<double>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<long double>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<std::string*>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<Trivial*>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<const std::string*>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<const Trivial*>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<std::string**>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<Trivial**>::value);

  // const qualified types are not assignable
  EXPECT_FALSE(absl::is_trivially_copy_assignable<const int>::value);

  // types with compiler generated copy assignment
  EXPECT_TRUE(absl::is_trivially_copy_assignable<Trivial>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<TrivialCopyAssign>::value);

  // Verify that types without them (i.e. nontrivial or deleted) are not.
  EXPECT_FALSE(absl::is_trivially_copy_assignable<NontrivialCopyAssign>::value);
  EXPECT_FALSE(absl::is_trivially_copy_assignable<DeletedCopyAssign>::value);
  EXPECT_FALSE(absl::is_trivially_copy_assignable<NonCopyable>::value);

  // types with vtables
  EXPECT_FALSE(absl::is_trivially_copy_assignable<Base>::value);

  // Verify that simple_pair is trivially assignable
  EXPECT_TRUE(
      (absl::is_trivially_copy_assignable<simple_pair<int, char*>>::value));
  EXPECT_TRUE(
      (absl::is_trivially_copy_assignable<simple_pair<int, Trivial>>::value));
  EXPECT_TRUE((absl::is_trivially_copy_assignable<
               simple_pair<int, TrivialCopyAssign>>::value));

  // Verify that types not trivially copy assignable are
  // correctly marked as such.
  EXPECT_FALSE(absl::is_trivially_copy_assignable<std::string>::value);
  EXPECT_FALSE(absl::is_trivially_copy_assignable<std::vector<int>>::value);

  // Verify that simple_pairs of types not trivially copy assignable
  // are not marked as trivial.
  EXPECT_FALSE((absl::is_trivially_copy_assignable<
                simple_pair<int, std::string>>::value));
  EXPECT_FALSE((absl::is_trivially_copy_assignable<
                simple_pair<std::string, int>>::value));

  // Verify that arrays are not trivially copy assignable
  using int10 = int[10];
  EXPECT_FALSE(absl::is_trivially_copy_assignable<int10>::value);

  // Verify that references are handled correctly
  EXPECT_TRUE(absl::is_trivially_copy_assignable<Trivial&&>::value);
  EXPECT_TRUE(absl::is_trivially_copy_assignable<Trivial&>::value);
}

#define ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(trait_name, ...)          \
  EXPECT_TRUE((std::is_same<typename std::trait_name<__VA_ARGS__>::type, \
                            absl::trait_name##_t<__VA_ARGS__>>::value))

TEST(TypeTraitsTest, TestRemoveCVAliases) {
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_cv, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_cv, const int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_cv, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_cv, const volatile int);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_const, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_const, const int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_const, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_const, const volatile int);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_volatile, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_volatile, const int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_volatile, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_volatile, const volatile int);
}

TEST(TypeTraitsTest, TestAddCVAliases) {
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_cv, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_cv, const int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_cv, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_cv, const volatile int);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_const, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_const, const int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_const, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_const, const volatile int);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_volatile, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_volatile, const int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_volatile, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_volatile, const volatile int);
}

TEST(TypeTraitsTest, TestReferenceAliases) {
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, volatile int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, int&&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_reference, volatile int&&);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, volatile int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, int&&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_lvalue_reference, volatile int&&);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, volatile int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, int&&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_rvalue_reference, volatile int&&);
}

TEST(TypeTraitsTest, TestPointerAliases) {
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_pointer, int*);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_pointer, volatile int*);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_pointer, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(add_pointer, volatile int);
}

TEST(TypeTraitsTest, TestSignednessAliases) {
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_signed, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_signed, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_signed, unsigned);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_signed, volatile unsigned);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_unsigned, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_unsigned, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_unsigned, unsigned);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(make_unsigned, volatile unsigned);
}

TEST(TypeTraitsTest, TestExtentAliases) {
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_extent, int[]);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_extent, int[1]);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_extent, int[1][1]);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_extent, int[][1]);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_all_extents, int[]);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_all_extents, int[1]);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_all_extents, int[1][1]);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(remove_all_extents, int[][1]);
}

TEST(TypeTraitsTest, TestAlignedStorageAlias) {
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 1);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 2);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 3);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 4);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 5);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 6);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 7);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 8);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 9);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 10);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 11);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 12);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 13);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 14);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 15);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 16);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 17);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 18);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 19);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 20);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 21);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 22);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 23);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 24);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 25);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 26);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 27);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 28);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 29);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 30);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 31);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 32);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 33);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 1, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 2, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 3, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 4, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 5, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 6, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 7, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 8, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 9, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 10, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 11, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 12, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 13, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 14, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 15, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 16, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 17, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 18, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 19, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 20, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 21, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 22, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 23, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 24, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 25, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 26, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 27, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 28, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 29, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 30, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 31, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 32, 128);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(aligned_storage, 33, 128);
}

TEST(TypeTraitsTest, TestDecay) {
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, volatile int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const volatile int);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, volatile int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const volatile int&);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, volatile int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, const volatile int&);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int[1]);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int[1][1]);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int[][1]);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int());
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int(float));  // NOLINT
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(decay, int(char, ...));  // NOLINT
}

struct TypeA {};
struct TypeB {};
struct TypeC {};
struct TypeD {};

template <typename T>
struct Wrap {};

enum class TypeEnum { A, B, C, D };

struct GetTypeT {
  template <typename T,
            absl::enable_if_t<std::is_same<T, TypeA>::value, int> = 0>
  TypeEnum operator()(Wrap<T>) const {
    return TypeEnum::A;
  }

  template <typename T,
            absl::enable_if_t<std::is_same<T, TypeB>::value, int> = 0>
  TypeEnum operator()(Wrap<T>) const {
    return TypeEnum::B;
  }

  template <typename T,
            absl::enable_if_t<std::is_same<T, TypeC>::value, int> = 0>
  TypeEnum operator()(Wrap<T>) const {
    return TypeEnum::C;
  }

  // NOTE: TypeD is intentionally not handled
} constexpr GetType = {};

TEST(TypeTraitsTest, TestEnableIf) {
  EXPECT_EQ(TypeEnum::A, GetType(Wrap<TypeA>()));
  EXPECT_EQ(TypeEnum::B, GetType(Wrap<TypeB>()));
  EXPECT_EQ(TypeEnum::C, GetType(Wrap<TypeC>()));
}

TEST(TypeTraitsTest, TestConditional) {
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(conditional, true, int, char);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(conditional, false, int, char);
}

// TODO(calabrese) Check with specialized std::common_type
TEST(TypeTraitsTest, TestCommonType) {
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int, char);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int, char, int);

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int, char&);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(common_type, int, char, int&);
}

TEST(TypeTraitsTest, TestUnderlyingType) {
  enum class enum_char : char {};
  enum class enum_long_long : long long {};  // NOLINT(runtime/int)

  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(underlying_type, enum_char);
  ABSL_INTERNAL_EXPECT_ALIAS_EQUIVALENCE(underlying_type, enum_long_long);
}

struct GetTypeExtT {
  template <typename T>
  absl::result_of_t<const GetTypeT&(T)> operator()(T&& arg) const {
    return GetType(std::forward<T>(arg));
  }

  TypeEnum operator()(Wrap<TypeD>) const { return TypeEnum::D; }
} constexpr GetTypeExt = {};

TEST(TypeTraitsTest, TestResultOf) {
  EXPECT_EQ(TypeEnum::A, GetTypeExt(Wrap<TypeA>()));
  EXPECT_EQ(TypeEnum::B, GetTypeExt(Wrap<TypeB>()));
  EXPECT_EQ(TypeEnum::C, GetTypeExt(Wrap<TypeC>()));
  EXPECT_EQ(TypeEnum::D, GetTypeExt(Wrap<TypeD>()));
}

template <typename T>
bool TestCopyAssign() {
  return absl::is_copy_assignable<T>::value ==
         std::is_copy_assignable<T>::value;
}

TEST(TypeTraitsTest, IsCopyAssignable) {
  EXPECT_TRUE(TestCopyAssign<int>());
  EXPECT_TRUE(TestCopyAssign<int&>());
  EXPECT_TRUE(TestCopyAssign<int&&>());

  struct S {};
  EXPECT_TRUE(TestCopyAssign<S>());
  EXPECT_TRUE(TestCopyAssign<S&>());
  EXPECT_TRUE(TestCopyAssign<S&&>());

  class C {
   public:
    explicit C(C* c) : c_(c) {}
    ~C() { delete c_; }

   private:
    C* c_;
  };
  EXPECT_TRUE(TestCopyAssign<C>());
  EXPECT_TRUE(TestCopyAssign<C&>());
  EXPECT_TRUE(TestCopyAssign<C&&>());

  // Reason for ifndef: add_lvalue_reference<T> in libc++ breaks for these cases
#ifndef _LIBCPP_VERSION
  EXPECT_TRUE(TestCopyAssign<int()>());
  EXPECT_TRUE(TestCopyAssign<int(int) const>());
  EXPECT_TRUE(TestCopyAssign<int(...) volatile&>());
  EXPECT_TRUE(TestCopyAssign<int(int, ...) const volatile&&>());
#endif  // _LIBCPP_VERSION
}

template <typename T>
bool TestMoveAssign() {
  return absl::is_move_assignable<T>::value ==
         std::is_move_assignable<T>::value;
}

TEST(TypeTraitsTest, IsMoveAssignable) {
  EXPECT_TRUE(TestMoveAssign<int>());
  EXPECT_TRUE(TestMoveAssign<int&>());
  EXPECT_TRUE(TestMoveAssign<int&&>());

  struct S {};
  EXPECT_TRUE(TestMoveAssign<S>());
  EXPECT_TRUE(TestMoveAssign<S&>());
  EXPECT_TRUE(TestMoveAssign<S&&>());

  class C {
   public:
    explicit C(C* c) : c_(c) {}
    ~C() { delete c_; }
    void operator=(const C&) = delete;
    void operator=(C&&) = delete;

   private:
    C* c_;
  };
  EXPECT_TRUE(TestMoveAssign<C>());
  EXPECT_TRUE(TestMoveAssign<C&>());
  EXPECT_TRUE(TestMoveAssign<C&&>());

  // Reason for ifndef: add_lvalue_reference<T> in libc++ breaks for these cases
#ifndef _LIBCPP_VERSION
  EXPECT_TRUE(TestMoveAssign<int()>());
  EXPECT_TRUE(TestMoveAssign<int(int) const>());
  EXPECT_TRUE(TestMoveAssign<int(...) volatile&>());
  EXPECT_TRUE(TestMoveAssign<int(int, ...) const volatile&&>());
#endif  // _LIBCPP_VERSION
}

}  // namespace