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___CONCEPTS_COMMON_WITH_H
10 #define _LIBCPP___CONCEPTS_COMMON_WITH_H
11 
12 #include <__concepts/common_reference_with.h>
13 #include <__concepts/same_as.h>
14 #include <__config>
15 #include <__type_traits/add_lvalue_reference.h>
16 #include <__type_traits/common_reference.h>
17 #include <__type_traits/common_type.h>
18 #include <__utility/declval.h>
19 
20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
21 #  pragma GCC system_header
22 #endif
23 
24 _LIBCPP_BEGIN_NAMESPACE_STD
25 
26 #if _LIBCPP_STD_VER > 17
27 
28 // [concept.common]
29 
30 template<class _Tp, class _Up>
31 concept common_with =
32   same_as<common_type_t<_Tp, _Up>, common_type_t<_Up, _Tp>> &&
33   requires {
34     static_cast<common_type_t<_Tp, _Up>>(std::declval<_Tp>());
35     static_cast<common_type_t<_Tp, _Up>>(std::declval<_Up>());
36   } &&
37   common_reference_with<
38     add_lvalue_reference_t<const _Tp>,
39     add_lvalue_reference_t<const _Up>> &&
40   common_reference_with<
41     add_lvalue_reference_t<common_type_t<_Tp, _Up>>,
42     common_reference_t<
43       add_lvalue_reference_t<const _Tp>,
44       add_lvalue_reference_t<const _Up>>>;
45 
46 #endif // _LIBCPP_STD_VER > 17
47 
48 _LIBCPP_END_NAMESPACE_STD
49 
50 #endif // _LIBCPP___CONCEPTS_COMMON_WITH_H
51