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.
27 template <class _Tp>
28 void __test_implicit_default_constructible(_Tp);
29 
30 template <class _Tp, class = void, class = typename is_default_constructible<_Tp>::type>
31 struct __is_implicitly_default_constructible
32     : false_type
33 { };
34 
35 template <class _Tp>
36 struct __is_implicitly_default_constructible<_Tp, decltype(std::__test_implicit_default_constructible<_Tp const&>({})), true_type>
37     : true_type
38 { };
39 
40 template <class _Tp>
41 struct __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