libcxx/test/support/unwrap_container_adaptor.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef SUPPORT_UNWRAP_CONTAINER_ADAPTOR_H
  10 #define SUPPORT_UNWRAP_CONTAINER_ADAPTOR_H
  11
  12 // Allows accessing the underlying container of the given adaptor.
  13 template <class Adaptor>
  14 struct UnwrapAdaptor : Adaptor {
  15   UnwrapAdaptor() = default;
  16
  17   UnwrapAdaptor(Adaptor&& adaptor) : Adaptor(std::move(adaptor)) {}
  18   // `c` is a protected member variable of the base class.
  19   decltype(auto) get_container() {
  20     return (UnwrapAdaptor::c); // Put into parentheses to make sure the function returns a reference.
  21   }
  22
  23   // TODO: make this work pre-C++20.
  24   decltype(auto) get_comparator()
  25   requires requires {
  26     UnwrapAdaptor::c;
  27   } {
  28     return (UnwrapAdaptor::comp); // Put into parentheses to make sure the function returns a reference.
  29   }
  30 };
  31
  32 #endif // SUPPORT_UNWRAP_CONTAINER_ADAPTOR_H