is_swappable_with.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2019 Tobias Hienzsch
 
#ifndef TETL_TYPE_TRAITS_IS_SWAPPABLE_WITH_HPP
#define TETL_TYPE_TRAITS_IS_SWAPPABLE_WITH_HPP
 
#include <etl/_cstddef/size_t.hpp>
#include <etl/_type_traits/add_lvalue_reference.hpp>
#include <etl/_type_traits/bool_constant.hpp>
#include <etl/_type_traits/conjunction.hpp>
#include <etl/_type_traits/declval.hpp>
#include <etl/_type_traits/is_move_assignable.hpp>
#include <etl/_type_traits/is_move_constructible.hpp>
#include <etl/_type_traits/is_nothrow_move_assignable.hpp>
#include <etl/_type_traits/is_nothrow_move_constructible.hpp>
#include <etl/_type_traits/void_t.hpp>
 
namespace etl {
 
template <typename T>
struct is_swappable;
 
template <typename T>
struct is_nothrow_swappable;
 
template <typename T>
    requires(etl::is_move_constructible_v<T> && etl::is_move_assignable_v<T>)
constexpr auto
swap(T& a, T& b) noexcept(etl::is_nothrow_move_constructible_v<T> && etl::is_nothrow_move_assignable_v<T>) -> void;
 
template <typename T, etl::size_t N>
    requires(etl::is_swappable<T>::value)
constexpr auto swap(T (&a)[N], T (&b)[N]) noexcept(etl::is_nothrow_swappable<T>::value) -> void;
 
// swap(declval<T>(), declval<U>()) is not valid
template <typename T, typename U, typename = void>
struct _swappable_with_helper : false_type { }; // NOLINT
 
// swap(declval<T>(), declval<U>()) is valid
template <typename T, typename U>
struct _swappable_with_helper<T, U, void_t<decltype(swap(declval<T>(), declval<U>()))>> : true_type { }; // NOLINT
 
// Determine if expressions with type and value category T and U can be
// swapped (and vice versa)
template <typename T, typename U>
struct is_swappable_with : bool_constant<conjunction_v<_swappable_with_helper<T, U>, _swappable_with_helper<U, T>>> { };
 
template <typename T, typename U>
inline constexpr bool is_swappable_with_v = is_swappable_with<T, U>::value;
 
} // namespace etl
 
#endif // TETL_TYPE_TRAITS_IS_SWAPPABLE_WITH_HPP