1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef _LIBCPP___TYPE_TRAITS_IS_IMPLICITLY_DEFAULT_CONSTRUCTIBLE_H
10#define _LIBCPP___TYPE_TRAITS_IS_IMPLICITLY_DEFAULT_CONSTRUCTIBLE_H
11
12#include <__config>
13#include <__type_traits/integral_constant.h>
14#include <__type_traits/is_default_constructible.h>
15
16#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17#  pragma GCC system_header
18#endif
19
20_LIBCPP_BEGIN_NAMESPACE_STD
21
22#ifndef _LIBCPP_CXX03_LANG
23// First of all, we can't implement this check in C++03 mode because the {}
24// default initialization syntax isn't valid.
25// Second, we implement the trait in a funny manner with two defaulted template
26// arguments to workaround Clang's PR43454.
27template <class _Tp>
28void __test_implicit_default_constructible(_Tp);
29
30template <class _Tp, class = void, class = typename is_default_constructible<_Tp>::type>
31struct __is_implicitly_default_constructible
32    : false_type
33{ };
34
35template <class _Tp>
36struct __is_implicitly_default_constructible<_Tp, decltype(std::__test_implicit_default_constructible<_Tp const&>({})), true_type>
37    : true_type
38{ };
39
40template <class _Tp>
41struct __is_implicitly_default_constructible<_Tp, decltype(std::__test_implicit_default_constructible<_Tp const&>({})), false_type>
42    : false_type
43{ };
44#endif // !C++03
45
46_LIBCPP_END_NAMESPACE_STD
47
48#endif // _LIBCPP___TYPE_TRAITS_IS_IMPLICITLY_DEFAULT_CONSTRUCTIBLE_H
49