1 //===-- declval utility -----------------------------------------*- C++ -*-===// 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 #ifndef LLVM_LIBC_SRC___SUPPORT_CPP_UTILITY_DECLVAL_H 9 #define LLVM_LIBC_SRC___SUPPORT_CPP_UTILITY_DECLVAL_H 10 11 #include "src/__support/CPP/type_traits/add_rvalue_reference.h" 12 #include "src/__support/CPP/type_traits/always_false.h" 13 #include "src/__support/macros/config.h" 14 15 namespace LIBC_NAMESPACE_DECL { 16 namespace cpp { 17 18 // declval declval()19template <typename T> cpp::add_rvalue_reference_t<T> declval() { 20 static_assert(cpp::always_false<T>, 21 "declval not allowed in an evaluated context"); 22 } 23 24 } // namespace cpp 25 } // namespace LIBC_NAMESPACE_DECL 26 27 #endif // LLVM_LIBC_SRC___SUPPORT_CPP_UTILITY_DECLVAL_H 28