| //===----------------------------------------------------------------------===// |
| // |
| // 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 |
