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