base/template_util.h

// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MINI_CHROMIUM_BASE_TEMPLATE_UTIL_H_
#define MINI_CHROMIUM_BASE_TEMPLATE_UTIL_H_

#include <stddef.h>

#include <type_traits>

namespace base {

namespace internal {

// Helper to express preferences in an overload set. If more than one overload
// are available for a given set of parameters the overload with the higher
// priority will be chosen.
template <size_t I>
struct priority_tag : priority_tag<I - 1> {};

template <>
struct priority_tag<0> {};

}  // namespace internal

// Implementation of C++20's std::remove_cvref.
//
// References:
// - https://en.cppreference.com/w/cpp/types/remove_cvref
// - https://wg21.link/meta.trans.other#lib:remove_cvref
template <typename T>
struct remove_cvref {
  using type = std::remove_cv_t<std::remove_reference_t<T>>;
};

// Implementation of C++20's std::remove_cvref_t.
//
// References:
// - https://en.cppreference.com/w/cpp/types/remove_cvref
// - https://wg21.link/meta.type.synop#lib:remove_cvref_t
template <typename T>
using remove_cvref_t = typename remove_cvref<T>::type;

// Simplified implementation of C++20's std::iter_reference_t.
// As opposed to std::iter_reference_t, this implementation does not restrict
// the type of `Iter`.
//
// Reference: https://wg21.link/iterator.synopsis#:~:text=iter_reference_t
template <typename Iter>
using iter_reference_t = decltype(*std::declval<Iter&>());

}  // namespace base

#endif  // MINI_CHROMIUM_BASE_TEMPLATE_UTIL_H_