llvm/libcxx/test/std/utilities/meta/meta.unary/meta.unary.cat/is_union.pass.cpp

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// type_traits

// is_union

#include <type_traits>
#include <cstddef>        // for std::nullptr_t
#include "test_macros.h"

template <class T>
void test_is_union()
{
    static_assert( std::is_union<T>::value, "");
    static_assert( std::is_union<const T>::value, "");
    static_assert( std::is_union<volatile T>::value, "");
    static_assert( std::is_union<const volatile T>::value, "");
#if TEST_STD_VER > 14
    static_assert( std::is_union_v<T>, "");
    static_assert( std::is_union_v<const T>, "");
    static_assert( std::is_union_v<volatile T>, "");
    static_assert( std::is_union_v<const volatile T>, "");
#endif
}

template <class T>
void test_is_not_union()
{
    static_assert(!std::is_union<T>::value, "");
    static_assert(!std::is_union<const T>::value, "");
    static_assert(!std::is_union<volatile T>::value, "");
    static_assert(!std::is_union<const volatile T>::value, "");
#if TEST_STD_VER > 14
    static_assert(!std::is_union_v<T>, "");
    static_assert(!std::is_union_v<const T>, "");
    static_assert(!std::is_union_v<volatile T>, "");
    static_assert(!std::is_union_v<const volatile T>, "");
#endif
}

class Empty
{
};

class NotEmpty
{
    virtual ~NotEmpty();
};

union Union {};

struct bit_zero
{
    int :  0;
};

class Abstract
{
    virtual ~Abstract() = 0;
};

enum Enum {zero, one};
struct incomplete_type;

typedef void (*FunctionPtr)();

int main(int, char**)
{
    test_is_union<Union>();

    test_is_not_union<std::nullptr_t>();
    test_is_not_union<void>();
    test_is_not_union<int>();
    test_is_not_union<int&>();
    test_is_not_union<int&&>();
    test_is_not_union<int*>();
    test_is_not_union<double>();
    test_is_not_union<const int*>();
    test_is_not_union<char[3]>();
    test_is_not_union<char[]>();
    test_is_not_union<Enum>();
    test_is_not_union<FunctionPtr>();
    test_is_not_union<Empty>();
    test_is_not_union<bit_zero>();
    test_is_not_union<NotEmpty>();
    test_is_not_union<Abstract>();
    test_is_not_union<incomplete_type>();

  return 0;
}