base/functional/identity.h

   1 // Copyright 2020 The Chromium Authors
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_FUNCTIONAL_IDENTITY_H_
   6 #define BASE_FUNCTIONAL_IDENTITY_H_
   7
   8 #include <utility>
   9
  10 namespace base {
  11
  12 // Implementation of C++20's std::identity.
  13 //
  14 // Reference:
  15 // - https://en.cppreference.com/w/cpp/utility/functional/identity
  16 // - https://wg21.link/func.identity
  17 struct identity {
  18   template <typename T>
  19   constexpr T&& operator()(T&& t) const noexcept {
  20     return std::forward<T>(t);
  21   }
  22
  23   using is_transparent = void;
  24 };
  25
  26 }  // namespace base
  27
  28 #endif  // BASE_FUNCTIONAL_IDENTITY_H_