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_REFERENCE_WITH_H
10 #define _LIBCPP___CONCEPTS_COMMON_REFERENCE_WITH_H
11 
12 #include <__concepts/convertible_to.h>
13 #include <__concepts/same_as.h>
14 #include <__config>
15 #include <__type_traits/common_reference.h>
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 >= 20
24 
25 // [concept.commonref]
26 
27 template <class _Tp, class _Up>
28 concept common_reference_with =
29     same_as<common_reference_t<_Tp, _Up>, common_reference_t<_Up, _Tp>> &&
30     convertible_to<_Tp, common_reference_t<_Tp, _Up>> && convertible_to<_Up, common_reference_t<_Tp, _Up>>;
31 
32 #endif // _LIBCPP_STD_VER >= 20
33 
34 _LIBCPP_END_NAMESPACE_STD
35 
36 #endif // _LIBCPP___CONCEPTS_COMMON_REFERENCE_WITH_H
37