1 /* 2 * Copyright (C) 2020 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef CHRE_UTIL_ALWAYS_FALSE_H_ 18 #define CHRE_UTIL_ALWAYS_FALSE_H_ 19 20 #include <type_traits> 21 22 namespace chre { 23 24 /** 25 * Simple helper which can be used when a type-dependent expression is needed 26 * that evaluates to false. Useful with static_assert in templates, for example: 27 * 28 * <code> 29 * template<typename T> 30 * class MyClass { 31 * static_assert(AlwaysFalse<T>::value, 32 * "Use one of the supported template specializations"); 33 * }; 34 * 35 * template<> 36 * class MyClass<int> { 37 * // (valid implementation) 38 * }; 39 * </code> 40 */ 41 template <typename... T> 42 struct AlwaysFalse : std::false_type {}; 43 44 } // namespace chre 45 46 #endif // CHRE_UTIL_ALWAYS_FALSE_H_ 47