sources/cxx-stl/llvm-libc++/test/std/utilities/memory/allocator.traits/allocator.traits.types/is_always_equal.pass.cpp

//===----------------------------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

// <memory>

// template <class Alloc>
// struct allocator_traits
// {
//   typedef Alloc::is_always_equal
//         | is_empty                     is_always_equal;
//     ...
// };

#include <memory>
#include <type_traits>

template <class T>
struct A
{
    typedef T value_type;
    typedef std::true_type is_always_equal;
};

template <class T>
struct B
{
    typedef T value_type;
};

template <class T>
struct C
{
    typedef T value_type;
	int not_empty_;  // some random member variable
};

int main()
{
    static_assert((std::is_same<std::allocator_traits<A<char> >::is_always_equal, std::true_type>::value), "");
    static_assert((std::is_same<std::allocator_traits<B<char> >::is_always_equal, std::true_type>::value), "");
    static_assert((std::is_same<std::allocator_traits<C<char> >::is_always_equal, std::false_type>::value), "");

    static_assert((std::is_same<std::allocator_traits<A<const char> >::is_always_equal, std::true_type>::value), "");
    static_assert((std::is_same<std::allocator_traits<B<const char> >::is_always_equal, std::true_type>::value), "");
    static_assert((std::is_same<std::allocator_traits<C<const char> >::is_always_equal, std::false_type>::value), "");
}