convertible_through_base.hpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef CONVERTIBLE_THROUGH_BASE_HPP
#define CONVERTIBLE_THROUGH_BASE_HPP
 
template <typename T>
concept ConvertibleThroughBase = requires(T const a) {
  typename T::BaseType;
  { a.base() } noexcept -> std::convertible_to<int64_t>;
};
concept ConvertibleThroughBase = requires(T const a) {…}
 
template <typename T, typename TTo>
concept ConvertibleThroughBaseOrTo = std::is_convertible_v<T, TTo> || ConvertibleThroughBase<T>;
 
template <typename Container, typename Index>
class TypedIndexContainer : public Container {
public:
  Container::reference at(size_t pos) { return this->Container::at(pos); }
  Container::reference at(const Index &pos) { return this->Container::at(pos.base()); }
 
  Container::const_reference at(size_t pos) const { return this->Container::at(pos); }
  Container::const_reference at(const Index &pos) const { return this->Container::at(pos.base()); }
 
  Container::reference operator[](size_t pos) { return this->Container::operator[](pos); }
  Container::reference operator[](const Index &pos) { return this->Container::operator[](pos.base()); }
 
  Container::const_reference operator[](size_t pos) const { return this->Container::operator[](pos); }
  Container::const_reference operator[](const Index &pos) const { return this->Container::operator[](pos.base()); }
};
class TypedIndexContainer : public Container {…};
 
#endif /* CONVERTIBLE_THROUGH_BASE_HPP */