// Copyright 2022 The Abseil Authors // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // https://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. #ifndef ABSL_STRINGS_HAS_ABSL_STRINGIFY_H_ #define ABSL_STRINGS_HAS_ABSL_STRINGIFY_H_ #include #include #include "absl/strings/string_view.h" namespace absl { ABSL_NAMESPACE_BEGIN namespace strings_internal { // This is an empty class not intended to be used. It exists so that // `HasAbslStringify` can reference a universal class rather than needing to be // copied for each new sink. class UnimplementedSink { public: void Append(size_t count, char ch); void Append(string_view v); // Support `absl::Format(&sink, format, args...)`. friend void AbslFormatFlush(UnimplementedSink* sink, absl::string_view v); }; } // namespace strings_internal // `HasAbslStringify` detects if type `T` supports the `AbslStringify()` // customization point (see // https://abseil.io/docs/cpp/guides/format#abslstringify for the // documentation). // // Note that there are types that can be `StrCat`-ed that do not use the // `AbslStringify` customization point (for example, `int`). template struct HasAbslStringify : std::false_type {}; template struct HasAbslStringify< T, std::enable_if_t(), std::declval()))>::value>> : std::true_type {}; ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_STRINGS_HAS_ABSL_STRINGIFY_H_