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diff --git a/absl/strings/internal/stringify_sink.h b/absl/strings/internal/stringify_sink.h
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+++ b/absl/strings/internal/stringify_sink.h
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+// 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_INTERNAL_STRINGIFY_SINK_H_
+#define ABSL_STRINGS_INTERNAL_STRINGIFY_SINK_H_
+
+#include <string>
+#include <type_traits>
+#include <utility>
+
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+namespace strings_internal {
+class StringifySink {
+ public:
+  void Append(size_t count, char ch);
+
+  void Append(string_view v);
+
+  bool PutPaddedString(string_view v, int width, int precision, bool left);
+
+  // Support `absl::Format(&sink, format, args...)`.
+  friend void AbslFormatFlush(StringifySink* sink, absl::string_view v) {
+    sink->Append(v);
+  }
+
+ private:
+  template <typename T>
+  friend string_view ExtractStringification(StringifySink& sink, const T& v);
+
+  std::string buffer_;
+};
+
+template <typename T>
+string_view ExtractStringification(StringifySink& sink, const T& v) {
+  AbslStringify(sink, v);
+  return sink.buffer_;
+}
+
+template <typename T, typename = void>
+struct HasAbslStringify : std::false_type {};
+
+template <typename T>
+struct HasAbslStringify<T, std::enable_if_t<std::is_void<decltype(AbslStringify(
+                               std::declval<strings_internal::StringifySink&>(),
+                               std::declval<const T&>()))>::value>>
+    : std::true_type {};
+
+}  // namespace strings_internal
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_INTERNAL_STRINGIFY_SINK_H_