libcxx/include/__concepts/common_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_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 >= 20
  27
  28 // [concept.common]
  29
  30 // clang-format off
  31 template <class _Tp, class _Up>
  32 concept common_with =
  33     same_as<common_type_t<_Tp, _Up>, common_type_t<_Up, _Tp>> &&
  34     requires {
  35         static_cast<common_type_t<_Tp, _Up>>(std::declval<_Tp>());
  36         static_cast<common_type_t<_Tp, _Up>>(std::declval<_Up>());
  37     } &&
  38     common_reference_with<
  39         add_lvalue_reference_t<const _Tp>,
  40         add_lvalue_reference_t<const _Up>> &&
  41     common_reference_with<
  42         add_lvalue_reference_t<common_type_t<_Tp, _Up>>,
  43         common_reference_t<
  44             add_lvalue_reference_t<const _Tp>,
  45             add_lvalue_reference_t<const _Up>>>;
  46 // clang-format on
  47
  48 #endif // _LIBCPP_STD_VER >= 20
  49
  50 _LIBCPP_END_NAMESPACE_STD
  51
  52 #endif // _LIBCPP___CONCEPTS_COMMON_WITH_H