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>
16 
17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
18 #  pragma GCC system_header
19 #endif
20 
21 _LIBCPP_BEGIN_NAMESPACE_STD
22 
23 #if _LIBCPP_STD_VER > 17
24 
25 // [concept.common]
26 
27 template<class _Tp, class _Up>
28 concept common_with =
29   same_as<common_type_t<_Tp, _Up>, common_type_t<_Up, _Tp>> &&
30   requires {
31     static_cast<common_type_t<_Tp, _Up>>(declval<_Tp>());
32     static_cast<common_type_t<_Tp, _Up>>(declval<_Up>());
33   } &&
34   common_reference_with<
35     add_lvalue_reference_t<const _Tp>,
36     add_lvalue_reference_t<const _Up>> &&
37   common_reference_with<
38     add_lvalue_reference_t<common_type_t<_Tp, _Up>>,
39     common_reference_t<
40       add_lvalue_reference_t<const _Tp>,
41       add_lvalue_reference_t<const _Up>>>;
42 
43 #endif // _LIBCPP_STD_VER > 17
44 
45 _LIBCPP_END_NAMESPACE_STD
46 
47 #endif // _LIBCPP___CONCEPTS_COMMON_WITH_H
48