v1/__utility/as_const.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___UTILITY_AS_CONST_H
0010 #define _LIBCPP___UTILITY_AS_CONST_H
0011
0012 #include <__config>
0013
0014 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0015 #  pragma GCC system_header
0016 #endif
0017
0018 _LIBCPP_BEGIN_NAMESPACE_STD
0019
0020 #if _LIBCPP_STD_VER >= 17
0021 template <class _Tp>
0022 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr const _Tp& as_const(_Tp& __t) noexcept {
0023   return __t;
0024 }
0025
0026 template <class _Tp>
0027 void as_const(const _Tp&&) = delete;
0028 #endif
0029
0030 _LIBCPP_END_NAMESPACE_STD
0031
0032 #endif // _LIBCPP___UTILITY_AS_CONST_H