libcxx/include/__concepts/common_reference_with.h

   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>
  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 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
  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>> &&
  31   convertible_to<_Up, common_reference_t<_Tp, _Up>>;
  32
  33 #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
  34
  35 _LIBCPP_END_NAMESPACE_STD
  36
  37 #endif // _LIBCPP___CONCEPTS_COMMON_REFERENCE_WITH_H