libcxx/include/__utility/as_const.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___UTILITY_AS_CONST_H
  10 #define _LIBCPP___UTILITY_AS_CONST_H
  11
  12 #include <__config>
  13 #include <__type_traits/add_const.h>
  14 #include <__utility/forward.h>
  15 #include <__utility/move.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 >= 17
  24 template <class _Tp>
  25 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr add_const_t<_Tp>& as_const(_Tp& __t) noexcept { return __t; }
  26
  27 template <class _Tp>
  28 void as_const(const _Tp&&) = delete;
  29 #endif
  30
  31 _LIBCPP_END_NAMESPACE_STD
  32
  33 #endif // _LIBCPP___UTILITY_AS_CONST_H