| //===----------------------------------------------------------------------===// | |
| // | |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | |
| // See https://llvm.org/LICENSE.txt for license information. | |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | |
| // | |
| //===----------------------------------------------------------------------===// | |
| #ifndef _LIBCPP___UTILITY_DECLVAL_H | |
| #define _LIBCPP___UTILITY_DECLVAL_H | |
| #include <__config> | |
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) | |
| # pragma GCC system_header | |
| #endif | |
| _LIBCPP_BEGIN_NAMESPACE_STD | |
| // Suppress deprecation notice for volatile-qualified return type resulting | |
| // from volatile-qualified types _Tp. | |
| _LIBCPP_SUPPRESS_DEPRECATED_PUSH | |
| template <class _Tp> | |
| _Tp&& __declval(int); | |
| template <class _Tp> | |
| _Tp __declval(long); | |
| _LIBCPP_SUPPRESS_DEPRECATED_POP | |
| template <class _Tp> | |
| _LIBCPP_HIDE_FROM_ABI decltype(std::__declval<_Tp>(0)) declval() _NOEXCEPT { | |
| static_assert(!__is_same(_Tp, _Tp), | |
| "std::declval can only be used in an unevaluated context. " | |
| "It's likely that your current usage is trying to extract a value from the function."); | |
| } | |
| _LIBCPP_END_NAMESPACE_STD | |
| #endif // _LIBCPP___UTILITY_DECLVAL_H |