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