STL/stl/inc/utility

// utility standard header (core)

// Copyright (c) Microsoft Corporation.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#ifndef _UTILITY_
#define _UTILITY_
#include <yvals_core.h>
#if _STL_COMPILER_PREPROCESSOR
#include <initializer_list>
#include <type_traits>

#if _HAS_CXX20
#include <compare>
#include <concepts>
#endif // _HAS_CXX20

#if _HAS_CXX23
#include <cstdlib>
#endif // _HAS_CXX23

#pragma pack(push, _CRT_PACKING)
#pragma warning(push, _STL_WARNING_LEVEL)
#pragma warning(disable : _STL_DISABLED_WARNINGS)
_STL_DISABLE_CLANG_WARNINGS
#pragma push_macro("new")
#undef new

// TRANSITION, non-_Ugly attribute tokens
#pragma push_macro("msvc")
#pragma push_macro("intrinsic")
#pragma push_macro("known_semantics")
#pragma push_macro("lifetimebound")
#undef msvc
#undef intrinsic
#undef known_semantics
#undef lifetimebound

_STD_BEGIN
_EXPORT_STD template <class _Ty, _Ty... _Vals>
struct integer_sequence { // sequence of integer parameters
    static_assert(is_integral_v<_Ty>, "integer_sequence<T, I...> requires T to be an integral type.");

    using value_type = _Ty;

    _NODISCARD static constexpr size_t size() noexcept {
        return sizeof...(_Vals);
    }
};

_EXPORT_STD template <class _Ty, _Ty _Size>
using make_integer_sequence = __make_integer_seq<integer_sequence, _Ty, _Size>;

_EXPORT_STD template <size_t... _Vals>
using index_sequence = integer_sequence<size_t, _Vals...>;

_EXPORT_STD template <size_t _Size>
using make_index_sequence = make_integer_sequence<size_t, _Size>;

_EXPORT_STD template <class... _Types>
using index_sequence_for = make_index_sequence<sizeof...(_Types)>;

_EXPORT_STD template <class _Ty, class _Pr>
_NODISCARD constexpr const _Ty&(max) (const _Ty& _Left _MSVC_LIFETIMEBOUND, const _Ty& _Right _MSVC_LIFETIMEBOUND,
    _Pr _Pred) noexcept(noexcept(_Pred(_Left, _Right))) /* strengthened */ {
    // return larger of _Left and _Right
    return _Pred(_Left, _Right) ? _Right : _Left;
}

#pragma warning(push)
#pragma warning(disable : 28285) // (syntax error in SAL annotation, occurs when _Ty is not an integral type)
_EXPORT_STD template <class _Ty>
_NODISCARD _Post_equal_to_(_Left < _Right ? _Right : _Left) constexpr const _Ty& //
    (max) (const _Ty& _Left _MSVC_LIFETIMEBOUND, const _Ty& _Right _MSVC_LIFETIMEBOUND)
        noexcept(noexcept(_Left < _Right)) /* strengthened */ {
    // return larger of _Left and _Right
    return _Left < _Right ? _Right : _Left;
}
#pragma warning(pop)

_EXPORT_STD template <class _Ty, class _Pr>
_NODISCARD constexpr _Ty(max)(initializer_list<_Ty>, _Pr); // implemented in <algorithm>

_EXPORT_STD template <class _Ty>
_NODISCARD constexpr _Ty(max)(initializer_list<_Ty>); // implemented in <algorithm>

_EXPORT_STD template <class _Ty, class _Pr>
_NODISCARD constexpr const _Ty&(min) (const _Ty& _Left _MSVC_LIFETIMEBOUND, const _Ty& _Right _MSVC_LIFETIMEBOUND,
    _Pr _Pred) noexcept(noexcept(_Pred(_Right, _Left))) /* strengthened */ {
    // return smaller of _Left and _Right
    return _Pred(_Right, _Left) ? _Right : _Left;
}

#pragma warning(push)
#pragma warning(disable : 28285) // (syntax error in SAL annotation, occurs when _Ty is not an integral type)
_EXPORT_STD template <class _Ty>
_NODISCARD _Post_equal_to_(_Right < _Left ? _Right : _Left) constexpr const _Ty& //
    (min) (const _Ty& _Left _MSVC_LIFETIMEBOUND, const _Ty& _Right _MSVC_LIFETIMEBOUND)
        noexcept(noexcept(_Right < _Left)) /* strengthened */ {
    // return smaller of _Left and _Right
    return _Right < _Left ? _Right : _Left;
}
#pragma warning(pop)

_EXPORT_STD template <class _Ty, class _Pr>
_NODISCARD constexpr _Ty(min)(initializer_list<_Ty>, _Pr); // implemented in <algorithm>

_EXPORT_STD template <class _Ty>
_NODISCARD constexpr _Ty(min)(initializer_list<_Ty>); // implemented in <algorithm>

_EXPORT_STD template <class _Ty, size_t _Size, enable_if_t<_Is_swappable<_Ty>::value, int> /* = 0 */>
_CONSTEXPR20 void swap(_Ty (&_Left)[_Size], _Ty (&_Right)[_Size]) noexcept(_Is_nothrow_swappable<_Ty>::value) {
    if (&_Left == &_Right) {
        return; // Handle self-swap as a no-op; see LWG-4165
    }

    if constexpr (_Is_trivially_swappable_v<_Ty>) {
        if (!_STD _Is_constant_evaluated()) {
            _STD _Swap_trivial_arrays(_Left, _Right);
            return;
        }
    }

    _Ty* _First1 = _Left;
    _Ty* _Last1  = _First1 + _Size;
    _Ty* _First2 = _Right;
    for (; _First1 != _Last1; ++_First1, ++_First2) {
        swap(*_First1, *_First2); // intentional ADL
    }
}

#if _HAS_CXX17
_EXPORT_STD template <class _Ty, enable_if_t<is_move_constructible_v<_Ty> && is_move_assignable_v<_Ty>, int> /* = 0 */>
#else // ^^^ _HAS_CXX17 / !_HAS_CXX17 vvv
template <class _Ty, int _Enabled /* = 0 */>
#endif // ^^^ !_HAS_CXX17 ^^^
_CONSTEXPR20 void swap(_Ty& _Left, _Ty& _Right)
    noexcept(is_nothrow_move_constructible_v<_Ty> && is_nothrow_move_assignable_v<_Ty>) {
    _Ty _Tmp = _STD move(_Left);
    _Left    = _STD move(_Right);
    _Right   = _STD move(_Tmp);
}

_EXPORT_STD struct piecewise_construct_t { // tag type for pair tuple arguments
    explicit piecewise_construct_t() = default;
};

_EXPORT_STD _INLINE_VAR constexpr piecewise_construct_t piecewise_construct{};

struct _Ignore { // struct that ignores assignments
    template <class _Ty>
    constexpr const _Ignore& operator=(const _Ty&) const noexcept {
        // do nothing
        return *this;
    }
};

_EXPORT_STD _INLINE_VAR constexpr _Ignore ignore{};

_EXPORT_STD template <class... _Types>
class tuple;

_EXPORT_STD template <class _Ty1, class _Ty2>
struct pair;

_EXPORT_STD template <class _Ty, size_t _Size>
class array;

_EXPORT_STD template <class _Tuple>
struct tuple_size;

_EXPORT_STD template <class _Ty>
constexpr size_t tuple_size_v = tuple_size<_Ty>::value;

_EXPORT_STD template <size_t _Index, class _Tuple>
struct tuple_element;

_EXPORT_STD template <size_t _Index, class _Tuple>
using tuple_element_t = typename tuple_element<_Index, _Tuple>::type;

template <size_t _Index, class... _Types>
_NODISCARD constexpr auto&& _Tuple_get(tuple<_Types...>&& _Tuple) noexcept;

_EXPORT_STD template <size_t _Index, class... _Types>
_NODISCARD constexpr tuple_element_t<_Index, tuple<_Types...>>& get(tuple<_Types...>& _Tuple) noexcept;

_EXPORT_STD template <size_t _Index, class... _Types>
_NODISCARD constexpr const tuple_element_t<_Index, tuple<_Types...>>& get(const tuple<_Types...>& _Tuple) noexcept;

_EXPORT_STD template <size_t _Index, class... _Types>
_NODISCARD constexpr tuple_element_t<_Index, tuple<_Types...>>&& get(tuple<_Types...>&& _Tuple) noexcept;

_EXPORT_STD template <size_t _Index, class... _Types>
_NODISCARD constexpr const tuple_element_t<_Index, tuple<_Types...>>&& get(const tuple<_Types...>&& _Tuple) noexcept;

_EXPORT_STD template <size_t _Idx, class _Ty, size_t _Size>
_NODISCARD constexpr _Ty& get(array<_Ty, _Size>& _Arr) noexcept;

_EXPORT_STD template <size_t _Idx, class _Ty, size_t _Size>
_NODISCARD constexpr const _Ty& get(const array<_Ty, _Size>& _Arr) noexcept;

_EXPORT_STD template <size_t _Idx, class _Ty, size_t _Size>
_NODISCARD constexpr _Ty&& get(array<_Ty, _Size>&& _Arr) noexcept;

_EXPORT_STD template <size_t _Idx, class _Ty, size_t _Size>
_NODISCARD constexpr const _Ty&& get(const array<_Ty, _Size>&& _Arr) noexcept;

#if _HAS_CXX20
template <class _Ty1, class _Ty2>
concept _Different_from = !same_as<remove_cvref_t<_Ty1>, remove_cvref_t<_Ty2>>;

template <class>
constexpr bool _Is_subrange_v = false;

#if _HAS_CXX23
template <class>
constexpr bool _Tuple_like_non_subrange_impl = false;

template <class... _Types>
constexpr bool _Tuple_like_non_subrange_impl<tuple<_Types...>> = true;

template <class _Ty1, class _Ty2>
constexpr bool _Tuple_like_non_subrange_impl<pair<_Ty1, _Ty2>> = true;

template <class _Ty, size_t _Size>
constexpr bool _Tuple_like_non_subrange_impl<array<_Ty, _Size>> = true;

template <class _Ty>
concept _Tuple_like_non_subrange = _Tuple_like_non_subrange_impl<remove_cvref_t<_Ty>>;

template <class _Ty>
concept _Tuple_like = _Tuple_like_non_subrange<_Ty> || _Is_subrange_v<remove_cvref_t<_Ty>>;

template <class _Ty>
concept _Pair_like_non_subrange = _Tuple_like_non_subrange<_Ty> && tuple_size_v<remove_cvref_t<_Ty>> == 2;

#ifdef __EDG__ // TRANSITION, VSO-1900279
template <class _PairLike, class _Ty1, class _Ty2>
concept _Can_construct_from_pair_like =
    _Pair_like_non_subrange<_PairLike> && is_constructible_v<_Ty1, decltype(_STD get<0>(_STD declval<_PairLike>()))>
    && is_constructible_v<_Ty2, decltype(_STD get<1>(_STD declval<_PairLike>()))>;
#endif // ^^^ workaround ^^^
#endif // _HAS_CXX23
#endif // _HAS_CXX20

_EXPORT_STD template <class _Ty1, class _Ty2>
struct pair { // store a pair of values
    using first_type  = _Ty1;
    using second_type = _Ty2;

    template <class _Uty1 = _Ty1, class _Uty2 = _Ty2,
        enable_if_t<conjunction_v<is_default_constructible<_Uty1>, is_default_constructible<_Uty2>>, int> = 0>
    constexpr explicit(
        !conjunction_v<_Is_implicitly_default_constructible<_Uty1>, _Is_implicitly_default_constructible<_Uty2>>) pair()
        noexcept(is_nothrow_default_constructible_v<_Uty1> && is_nothrow_default_constructible_v<_Uty2>) // strengthened
        : first(), second() {}

    template <class _Uty1 = _Ty1, class _Uty2 = _Ty2,
        enable_if_t<conjunction_v<is_copy_constructible<_Uty1>, is_copy_constructible<_Uty2>>, int> = 0>
    constexpr explicit(!conjunction_v<is_convertible<const _Uty1&, _Uty1>, is_convertible<const _Uty2&, _Uty2>>)
        pair(const _Ty1& _Val1, const _Ty2& _Val2)
            noexcept(is_nothrow_copy_constructible_v<_Uty1> && is_nothrow_copy_constructible_v<_Uty2>) // strengthened
        : first(_Val1), second(_Val2) {}

#if _HAS_CXX23
    template <class _Other1 = _Ty1, class _Other2 = _Ty2,
#else // ^^^ _HAS_CXX23 / !_HAS_CXX23 vvv
    template <class _Other1, class _Other2,
#endif // ^^^ !_HAS_CXX23 ^^^
        enable_if_t<conjunction_v<is_constructible<_Ty1, _Other1>, is_constructible<_Ty2, _Other2>>, int> = 0>
    constexpr explicit(!conjunction_v<is_convertible<_Other1, _Ty1>, is_convertible<_Other2, _Ty2>>)
        pair(_Other1&& _Val1, _Other2&& _Val2) noexcept(
            is_nothrow_constructible_v<_Ty1, _Other1> && is_nothrow_constructible_v<_Ty2, _Other2>) // strengthened
        : first(_STD forward<_Other1>(_Val1)), second(_STD forward<_Other2>(_Val2)) {
    }

    pair(const pair&) = default;
    pair(pair&&)      = default;

#if _HAS_CXX23
    template <class _Other1, class _Other2>
        requires is_constructible_v<_Ty1, _Other1&> && is_constructible_v<_Ty2, _Other2&>
    constexpr explicit(!conjunction_v<is_convertible<_Other1&, _Ty1>, is_convertible<_Other2&, _Ty2>>)
        pair(pair<_Other1, _Other2>& _Right) noexcept(
            is_nothrow_constructible_v<_Ty1, _Other1&> && is_nothrow_constructible_v<_Ty2, _Other2&>) // strengthened
        : first(_Right.first), second(_Right.second) {}
#endif // _HAS_CXX23

    template <class _Other1, class _Other2,
        enable_if_t<conjunction_v<is_constructible<_Ty1, const _Other1&>, is_constructible<_Ty2, const _Other2&>>,
            int> = 0>
    constexpr explicit(!conjunction_v<is_convertible<const _Other1&, _Ty1>, is_convertible<const _Other2&, _Ty2>>)
        pair(const pair<_Other1, _Other2>& _Right)
            noexcept(is_nothrow_constructible_v<_Ty1, const _Other1&>
                     && is_nothrow_constructible_v<_Ty2, const _Other2&>) // strengthened
        : first(_Right.first), second(_Right.second) {}

    template <class _Other1, class _Other2,
        enable_if_t<conjunction_v<is_constructible<_Ty1, _Other1>, is_constructible<_Ty2, _Other2>>, int> = 0>
    constexpr explicit(!conjunction_v<is_convertible<_Other1, _Ty1>, is_convertible<_Other2, _Ty2>>)
        pair(pair<_Other1, _Other2>&& _Right) noexcept(
            is_nothrow_constructible_v<_Ty1, _Other1> && is_nothrow_constructible_v<_Ty2, _Other2>) // strengthened
        : first(_STD forward<_Other1>(_Right.first)), second(_STD forward<_Other2>(_Right.second)) {}

#if _HAS_CXX23
    template <class _Other1, class _Other2>
        requires is_constructible_v<_Ty1, const _Other1> && is_constructible_v<_Ty2, const _Other2>
    constexpr explicit(!conjunction_v<is_convertible<const _Other1, _Ty1>, is_convertible<const _Other2, _Ty2>>)
        pair(const pair<_Other1, _Other2>&& _Right)
            noexcept(is_nothrow_constructible_v<_Ty1, const _Other1>
                     && is_nothrow_constructible_v<_Ty2, const _Other2>) // strengthened
        : first(_STD forward<const _Other1>(_Right.first)), second(_STD forward<const _Other2>(_Right.second)) {}

#ifdef __EDG__ // TRANSITION, VSO-1900279
    template <class _Other, enable_if_t<_Can_construct_from_pair_like<_Other, _Ty1, _Ty2>, int> = 0>
#else // ^^^ workaround / no workaround vvv
    template <_Pair_like_non_subrange _Other>
        requires conjunction_v<is_constructible<_Ty1, decltype(_STD get<0>(_STD declval<_Other>()))>,
                     is_constructible<_Ty2, decltype(_STD get<1>(_STD declval<_Other>()))>>
#endif // ^^^ no workaround ^^^
    constexpr explicit(!conjunction_v<is_convertible<decltype(_STD get<0>(_STD declval<_Other>())), _Ty1>,
                       is_convertible<decltype(_STD get<1>(_STD declval<_Other>())), _Ty2>>) pair(_Other&& _Right)
        noexcept(is_nothrow_constructible_v<_Ty1, decltype(_STD get<0>(_STD declval<_Other>()))>
                 && is_nothrow_constructible_v<_Ty2, decltype(_STD get<1>(_STD declval<_Other>()))>) // strengthened
        : first(_STD get<0>(_STD forward<_Other>(_Right))), second(_STD get<1>(_STD forward<_Other>(_Right))) {
    }
#endif // _HAS_CXX23

    template <class... _Types1, class... _Types2>
    _CONSTEXPR20 pair(piecewise_construct_t, tuple<_Types1...> _Val1, tuple<_Types2...> _Val2)
        : pair(_Val1, _Val2, index_sequence_for<_Types1...>{}, index_sequence_for<_Types2...>{}) {}

    pair& operator=(const volatile pair&) = delete;

    template <class _Myself = pair,
        enable_if_t<conjunction_v<_Is_copy_assignable_no_precondition_check<typename _Myself::first_type>,
                        _Is_copy_assignable_no_precondition_check<typename _Myself::second_type>>,
            int>            = 0>
    _CONSTEXPR20 pair& operator=(_Identity_t<const _Myself&> _Right)
        noexcept(conjunction_v<is_nothrow_copy_assignable<_Ty1>, is_nothrow_copy_assignable<_Ty2>>) /* strengthened */ {
        first  = _Right.first;
        second = _Right.second;
        return *this;
    }

#if _HAS_CXX23
    template <class _Myself = pair>
        requires _Is_copy_assignable_unchecked_v<const typename _Myself::first_type>
              && _Is_copy_assignable_unchecked_v<const typename _Myself::second_type>
    constexpr const pair& operator=(_Identity_t<const _Myself&> _Right) const
        noexcept(conjunction_v<is_nothrow_copy_assignable<const _Ty1>,
            is_nothrow_copy_assignable<const _Ty2>>) /* strengthened */ {
        first  = _Right.first;
        second = _Right.second;
        return *this;
    }
#endif // _HAS_CXX23

    template <class _Myself = pair,
        enable_if_t<conjunction_v<_Is_move_assignable_no_precondition_check<typename _Myself::first_type>,
                        _Is_move_assignable_no_precondition_check<typename _Myself::second_type>>,
            int>            = 0>
    _CONSTEXPR20 pair& operator=(_Identity_t<_Myself&&> _Right)
        noexcept(conjunction_v<is_nothrow_move_assignable<_Ty1>, is_nothrow_move_assignable<_Ty2>>) /* strengthened */ {
        first  = _STD forward<_Ty1>(_Right.first);
        second = _STD forward<_Ty2>(_Right.second);
        return *this;
    }

#if _HAS_CXX23
    template <class _Myself = pair>
        requires _Is_assignable_no_precondition_check<const typename _Myself::first_type&, _Ty1>::value
              && _Is_assignable_no_precondition_check<const typename _Myself::second_type&, _Ty2>::value
    constexpr const pair& operator=(_Identity_t<_Myself&&> _Right) const
        noexcept(conjunction_v<is_nothrow_assignable<const _Ty1&, _Ty1>,
            is_nothrow_assignable<const _Ty2&, _Ty2>>) /* strengthened */ {
        first  = _STD forward<_Ty1>(_Right.first);
        second = _STD forward<_Ty2>(_Right.second);
        return *this;
    }
#endif // _HAS_CXX23

    template <class _Other1, class _Other2,
        enable_if_t<conjunction_v<negation<is_same<pair, pair<_Other1, _Other2>>>, is_assignable<_Ty1&, const _Other1&>,
                        is_assignable<_Ty2&, const _Other2&>>,
            int> = 0>
    _CONSTEXPR20 pair& operator=(const pair<_Other1, _Other2>& _Right)
        noexcept(is_nothrow_assignable_v<_Ty1&, const _Other1&>
                 && is_nothrow_assignable_v<_Ty2&, const _Other2&>) /* strengthened */ {
        first  = _Right.first;
        second = _Right.second;
        return *this;
    }

#if _HAS_CXX23
    template <class _Other1, class _Other2>
        requires (!is_same_v<pair, pair<_Other1, _Other2>>)
              && is_assignable_v<const _Ty1&, const _Other1&> && is_assignable_v<const _Ty2&, const _Other2&>
    constexpr const pair& operator=(const pair<_Other1, _Other2>& _Right) const
        noexcept(is_nothrow_assignable_v<const _Ty1&, const _Other1&>
                 && is_nothrow_assignable_v<const _Ty2&, const _Other2&>) /* strengthened */ {
        first  = _Right.first;
        second = _Right.second;
        return *this;
    }
#endif // _HAS_CXX23

    template <class _Other1, class _Other2,
        enable_if_t<conjunction_v<negation<is_same<pair, pair<_Other1, _Other2>>>, is_assignable<_Ty1&, _Other1>,
                        is_assignable<_Ty2&, _Other2>>,
            int> = 0>
    _CONSTEXPR20 pair& operator=(pair<_Other1, _Other2>&& _Right) noexcept(
        is_nothrow_assignable_v<_Ty1&, _Other1> && is_nothrow_assignable_v<_Ty2&, _Other2>) /* strengthened */ {
        first  = _STD forward<_Other1>(_Right.first);
        second = _STD forward<_Other2>(_Right.second);
        return *this;
    }

#if _HAS_CXX23
    template <class _Other1, class _Other2>
        requires (!is_same_v<pair, pair<_Other1, _Other2>>)
              && is_assignable_v<const _Ty1&, _Other1> && is_assignable_v<const _Ty2&, _Other2>
    constexpr const pair& operator=(pair<_Other1, _Other2>&& _Right) const
        noexcept(is_nothrow_assignable_v<const _Ty1&, _Other1>
                 && is_nothrow_assignable_v<const _Ty2&, _Other2>) /* strengthened */ {
        first  = _STD forward<_Other1>(_Right.first);
        second = _STD forward<_Other2>(_Right.second);
        return *this;
    }

    template <_Pair_like_non_subrange _Other>
        requires _Different_from<_Other, pair> && is_assignable_v<_Ty1&, decltype(_STD get<0>(_STD declval<_Other>()))>
              && is_assignable_v<_Ty2&, decltype(_STD get<1>(_STD declval<_Other>()))>
    constexpr pair& operator=(_Other&& _Right)
        noexcept(is_nothrow_assignable_v<_Ty1&, decltype(_STD get<0>(_STD declval<_Other>()))>
                 && is_nothrow_assignable_v<_Ty2&, decltype(_STD get<1>(_STD declval<_Other>()))>) /* strengthened */ {
        first  = _STD get<0>(_STD forward<_Other>(_Right));
        second = _STD get<1>(_STD forward<_Other>(_Right));
        return *this;
    }

    template <_Pair_like_non_subrange _Other>
        requires _Different_from<_Other, pair>
              && is_assignable_v<const _Ty1&, decltype(_STD get<0>(_STD declval<_Other>()))>
              && is_assignable_v<const _Ty2&, decltype(_STD get<1>(_STD declval<_Other>()))>
    constexpr const pair& operator=(_Other&& _Right) const noexcept(
        is_nothrow_assignable_v<const _Ty1&, decltype(_STD get<0>(_STD declval<_Other>()))>
        && is_nothrow_assignable_v<const _Ty2&, decltype(_STD get<1>(_STD declval<_Other>()))>) /* strengthened */ {
        first  = _STD get<0>(_STD forward<_Other>(_Right));
        second = _STD get<1>(_STD forward<_Other>(_Right));
        return *this;
    }
#endif // _HAS_CXX23

    _CONSTEXPR20 void swap(pair& _Right)
        noexcept(_Is_nothrow_swappable<_Ty1>::value && _Is_nothrow_swappable<_Ty2>::value) {
        using _STD swap;
        swap(first, _Right.first); // intentional ADL
        swap(second, _Right.second); // intentional ADL
    }

#if _HAS_CXX23
    template <int = 0> // see GH-3013
    constexpr void swap(const pair& _Right) const
        noexcept(is_nothrow_swappable_v<const _Ty1> && is_nothrow_swappable_v<const _Ty2>) {
        using _STD swap;
        swap(first, _Right.first); // intentional ADL
        swap(second, _Right.second); // intentional ADL
    }
#endif // _HAS_CXX23

    _Ty1 first; // the first stored value
    _Ty2 second; // the second stored value

private:
    template <class _Tuple1, class _Tuple2, size_t... _Indices1, size_t... _Indices2>
    constexpr pair(_Tuple1& _Val1, _Tuple2& _Val2, index_sequence<_Indices1...>, index_sequence<_Indices2...>)
        : first(_STD _Tuple_get<_Indices1>(_STD move(_Val1))...),
          second(_STD _Tuple_get<_Indices2>(_STD move(_Val2))...) {}
};

#if _HAS_CXX17
template <class _Ty1, class _Ty2>
pair(_Ty1, _Ty2) -> pair<_Ty1, _Ty2>;
#endif // _HAS_CXX17

_EXPORT_STD template <class _Ty1, class _Ty2,
    enable_if_t<_Is_swappable<_Ty1>::value && _Is_swappable<_Ty2>::value, int> = 0>
_CONSTEXPR20 void swap(pair<_Ty1, _Ty2>& _Left, pair<_Ty1, _Ty2>& _Right) noexcept(noexcept(_Left.swap(_Right))) {
    _Left.swap(_Right);
}

#if _HAS_CXX23
_EXPORT_STD template <class _Ty1, class _Ty2>
    requires is_swappable<const _Ty1>::value && is_swappable<const _Ty2>::value // TRANSITION, /permissive needs ::value
constexpr void swap(const pair<_Ty1, _Ty2>& _Left, const pair<_Ty1, _Ty2>& _Right)
    noexcept(noexcept(_Left.swap(_Right))) {
    _Left.swap(_Right);
}
#endif // _HAS_CXX23

_EXPORT_STD template <class _Ty1, class _Ty2, class _Uty1, class _Uty2>
_NODISCARD constexpr bool operator==(const pair<_Ty1, _Ty2>& _Left, const pair<_Uty1, _Uty2>& _Right) {
    return _Left.first == _Right.first && _Left.second == _Right.second;
}

#if _HAS_CXX20
_EXPORT_STD template <class _Ty1, class _Ty2, class _Uty1, class _Uty2>
_NODISCARD constexpr common_comparison_category_t<_Synth_three_way_result<_Ty1, _Uty1>,
    _Synth_three_way_result<_Ty2, _Uty2>>
    operator<=>(const pair<_Ty1, _Ty2>& _Left, const pair<_Uty1, _Uty2>& _Right) {
    if (auto _Result = _Synth_three_way{}(_Left.first, _Right.first); _Result != 0) {
        return _Result;
    }
    return _Synth_three_way{}(_Left.second, _Right.second);
}
#else // ^^^ _HAS_CXX20 / !_HAS_CXX20 vvv
template <class _Ty1, class _Ty2, class _Uty1, class _Uty2>
_NODISCARD constexpr bool operator!=(const pair<_Ty1, _Ty2>& _Left, const pair<_Uty1, _Uty2>& _Right) {
    return !(_Left == _Right);
}

template <class _Ty1, class _Ty2, class _Uty1, class _Uty2>
_NODISCARD constexpr bool operator<(const pair<_Ty1, _Ty2>& _Left, const pair<_Uty1, _Uty2>& _Right) {
    return _Left.first < _Right.first || (!(_Right.first < _Left.first) && _Left.second < _Right.second);
}

template <class _Ty1, class _Ty2, class _Uty1, class _Uty2>
_NODISCARD constexpr bool operator>(const pair<_Ty1, _Ty2>& _Left, const pair<_Uty1, _Uty2>& _Right) {
    return _Right < _Left;
}

template <class _Ty1, class _Ty2, class _Uty1, class _Uty2>
_NODISCARD constexpr bool operator<=(const pair<_Ty1, _Ty2>& _Left, const pair<_Uty1, _Uty2>& _Right) {
    return !(_Right < _Left);
}

template <class _Ty1, class _Ty2, class _Uty1, class _Uty2>
_NODISCARD constexpr bool operator>=(const pair<_Ty1, _Ty2>& _Left, const pair<_Uty1, _Uty2>& _Right) {
    return !(_Left < _Right);
}
#endif // ^^^ !_HAS_CXX20 ^^^

#if _HAS_CXX23
template <class _Ty1, class _Ty2, class _Uty1, class _Uty2, template <class> class _TQual,
    template <class> class _UQual>
    requires requires {
        typename pair<common_reference_t<_TQual<_Ty1>, _UQual<_Uty1>>, common_reference_t<_TQual<_Ty2>, _UQual<_Uty2>>>;
    }
struct basic_common_reference<pair<_Ty1, _Ty2>, pair<_Uty1, _Uty2>, _TQual, _UQual> {
    using type = pair<common_reference_t<_TQual<_Ty1>, _UQual<_Uty1>>, common_reference_t<_TQual<_Ty2>, _UQual<_Uty2>>>;
};

template <class _Ty1, class _Ty2, class _Uty1, class _Uty2>
    requires requires { typename pair<common_type_t<_Ty1, _Uty1>, common_type_t<_Ty2, _Uty2>>; }
struct common_type<pair<_Ty1, _Ty2>, pair<_Uty1, _Uty2>> {
    using type = pair<common_type_t<_Ty1, _Uty1>, common_type_t<_Ty2, _Uty2>>;
};
#endif // _HAS_CXX23

template <class _Ty>
struct _Unrefwrap_helper { // leave unchanged if not a reference_wrapper
    using type = _Ty;
};

template <class _Ty>
struct _Unrefwrap_helper<reference_wrapper<_Ty>> { // make a reference from a reference_wrapper
    using type = _Ty&;
};

// decay, then unwrap a reference_wrapper
template <class _Ty>
using _Unrefwrap_t = typename _Unrefwrap_helper<decay_t<_Ty>>::type;

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr pair<_Unrefwrap_t<_Ty1>, _Unrefwrap_t<_Ty2>> make_pair(_Ty1&& _Val1, _Ty2&& _Val2)
    noexcept(is_nothrow_constructible_v<_Unrefwrap_t<_Ty1>, _Ty1>
             && is_nothrow_constructible_v<_Unrefwrap_t<_Ty2>, _Ty2>) /* strengthened */ {
    // return pair composed from arguments
    using _Mypair = pair<_Unrefwrap_t<_Ty1>, _Unrefwrap_t<_Ty2>>;
    return _Mypair(_STD forward<_Ty1>(_Val1), _STD forward<_Ty2>(_Val2));
}

namespace _CXX20_DEPRECATE_REL_OPS rel_ops {
    _EXPORT_STD template <class _Ty>
    _CXX20_DEPRECATE_REL_OPS _NODISCARD bool operator!=(const _Ty& _Left, const _Ty& _Right) {
        return !(_Left == _Right);
    }

    _EXPORT_STD template <class _Ty>
    _CXX20_DEPRECATE_REL_OPS _NODISCARD bool operator>(const _Ty& _Left, const _Ty& _Right) {
        return _Right < _Left;
    }

    _EXPORT_STD template <class _Ty>
    _CXX20_DEPRECATE_REL_OPS _NODISCARD bool operator<=(const _Ty& _Left, const _Ty& _Right) {
        return !(_Right < _Left);
    }

    _EXPORT_STD template <class _Ty>
    _CXX20_DEPRECATE_REL_OPS _NODISCARD bool operator>=(const _Ty& _Left, const _Ty& _Right) {
        return !(_Left < _Right);
    }
} // namespace _CXX20_DEPRECATE_REL_OPS rel_ops

template <class _Tuple, class = void>
struct _Tuple_size_sfinae {}; // selected when tuple_size<_Tuple>::value isn't well-formed

template <class _Tuple>
struct _Tuple_size_sfinae<_Tuple, void_t<decltype(tuple_size<_Tuple>::value)>>
    : integral_constant<size_t, tuple_size<_Tuple>::value> {}; // selected when tuple_size<_Tuple>::value is well-formed

template <class _Tuple>
struct tuple_size<const _Tuple> : _Tuple_size_sfinae<_Tuple> {}; // ignore cv

template <class _Tuple>
struct _CXX20_DEPRECATE_VOLATILE tuple_size<volatile _Tuple> : _Tuple_size_sfinae<_Tuple> {}; // ignore cv

template <class _Tuple>
struct _CXX20_DEPRECATE_VOLATILE tuple_size<const volatile _Tuple> : _Tuple_size_sfinae<_Tuple> {}; // ignore cv

template <size_t _Index, class _Tuple>
struct _MSVC_KNOWN_SEMANTICS tuple_element<_Index, const _Tuple> : tuple_element<_Index, _Tuple> {
    using _Mybase = tuple_element<_Index, _Tuple>;
    using type    = add_const_t<typename _Mybase::type>;
};

template <size_t _Index, class _Tuple>
struct _CXX20_DEPRECATE_VOLATILE _MSVC_KNOWN_SEMANTICS tuple_element<_Index, volatile _Tuple>
    : tuple_element<_Index, _Tuple> {
    using _Mybase = tuple_element<_Index, _Tuple>;
    using type    = add_volatile_t<typename _Mybase::type>;
};

template <size_t _Index, class _Tuple>
struct _CXX20_DEPRECATE_VOLATILE _MSVC_KNOWN_SEMANTICS tuple_element<_Index, const volatile _Tuple>
    : tuple_element<_Index, _Tuple> {
    using _Mybase = tuple_element<_Index, _Tuple>;
    using type    = add_cv_t<typename _Mybase::type>;
};

template <class _Ty, size_t _Size>
struct tuple_size<array<_Ty, _Size>> : integral_constant<size_t, _Size> {}; // size of array

template <size_t _Idx, class _Ty, size_t _Size>
struct _MSVC_KNOWN_SEMANTICS tuple_element<_Idx, array<_Ty, _Size>> {
    static_assert(_Idx < _Size, "array index out of bounds");

    using type = _Ty;
};

template <class... _Types>
struct tuple_size<tuple<_Types...>> : integral_constant<size_t, sizeof...(_Types)> {}; // size of tuple

template <size_t _Index>
struct _MSVC_KNOWN_SEMANTICS tuple_element<_Index, tuple<>> { // enforce bounds checking
    static_assert(_Always_false<integral_constant<size_t, _Index>>, "tuple index out of bounds");
};

template <class _This, class... _Rest>
struct _MSVC_KNOWN_SEMANTICS tuple_element<0, tuple<_This, _Rest...>> { // select first element
    using type = _This;
    // MSVC assumes the meaning of _Ttype; remove or rename, but do not change semantics
    using _Ttype = tuple<_This, _Rest...>;
};

template <size_t _Index, class _This, class... _Rest>
struct _MSVC_KNOWN_SEMANTICS tuple_element<_Index, tuple<_This, _Rest...>>
    : tuple_element<_Index - 1, tuple<_Rest...>> {}; // recursive tuple_element definition

template <class _Ty1, class _Ty2>
struct tuple_size<pair<_Ty1, _Ty2>> : integral_constant<size_t, 2> {}; // size of pair

template <size_t _Idx, class _Ty1, class _Ty2>
struct _MSVC_KNOWN_SEMANTICS tuple_element<_Idx, pair<_Ty1, _Ty2>> {
    static_assert(_Idx < 2, "pair index out of bounds");

    using type = conditional_t<_Idx == 0, _Ty1, _Ty2>;
};

_EXPORT_STD template <size_t _Idx, class _Ty1, class _Ty2>
_NODISCARD constexpr tuple_element_t<_Idx, pair<_Ty1, _Ty2>>& get(pair<_Ty1, _Ty2>& _Pr) noexcept {
    // get reference to element at _Idx in pair _Pr
    if constexpr (_Idx == 0) {
        return _Pr.first;
    } else {
        return _Pr.second;
    }
}

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr _Ty1& get(pair<_Ty1, _Ty2>& _Pr) noexcept {
    // get reference to element _Ty1 in pair _Pr
    return _Pr.first;
}

_EXPORT_STD template <class _Ty2, class _Ty1>
_NODISCARD constexpr _Ty2& get(pair<_Ty1, _Ty2>& _Pr) noexcept {
    // get reference to element _Ty2 in pair _Pr
    return _Pr.second;
}

_EXPORT_STD template <size_t _Idx, class _Ty1, class _Ty2>
_NODISCARD constexpr const tuple_element_t<_Idx, pair<_Ty1, _Ty2>>& get(const pair<_Ty1, _Ty2>& _Pr) noexcept {
    // get const reference to element at _Idx in pair _Pr
    if constexpr (_Idx == 0) {
        return _Pr.first;
    } else {
        return _Pr.second;
    }
}

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr const _Ty1& get(const pair<_Ty1, _Ty2>& _Pr) noexcept {
    // get const reference to element _Ty1 in pair _Pr
    return _Pr.first;
}

_EXPORT_STD template <class _Ty2, class _Ty1>
_NODISCARD constexpr const _Ty2& get(const pair<_Ty1, _Ty2>& _Pr) noexcept {
    // get const reference to element _Ty2 in pair _Pr
    return _Pr.second;
}

_EXPORT_STD template <size_t _Idx, class _Ty1, class _Ty2>
_NODISCARD constexpr tuple_element_t<_Idx, pair<_Ty1, _Ty2>>&& get(pair<_Ty1, _Ty2>&& _Pr) noexcept {
    // get rvalue reference to element at _Idx in pair _Pr
    if constexpr (_Idx == 0) {
        return _STD forward<_Ty1>(_Pr.first);
    } else {
        return _STD forward<_Ty2>(_Pr.second);
    }
}

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr _Ty1&& get(pair<_Ty1, _Ty2>&& _Pr) noexcept {
    // get rvalue reference to element _Ty1 in pair _Pr
    return _STD forward<_Ty1>(_Pr.first);
}

_EXPORT_STD template <class _Ty2, class _Ty1>
_NODISCARD constexpr _Ty2&& get(pair<_Ty1, _Ty2>&& _Pr) noexcept {
    // get rvalue reference to element _Ty2 in pair _Pr
    return _STD forward<_Ty2>(_Pr.second);
}

_EXPORT_STD template <size_t _Idx, class _Ty1, class _Ty2>
_NODISCARD constexpr const tuple_element_t<_Idx, pair<_Ty1, _Ty2>>&& get(const pair<_Ty1, _Ty2>&& _Pr) noexcept {
    // get const rvalue reference to element at _Idx in pair _Pr
    if constexpr (_Idx == 0) {
        return _STD forward<const _Ty1>(_Pr.first);
    } else {
        return _STD forward<const _Ty2>(_Pr.second);
    }
}

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr const _Ty1&& get(const pair<_Ty1, _Ty2>&& _Pr) noexcept {
    // get const rvalue reference to element _Ty1 in pair _Pr
    return _STD forward<const _Ty1>(_Pr.first);
}

_EXPORT_STD template <class _Ty2, class _Ty1>
_NODISCARD constexpr const _Ty2&& get(const pair<_Ty1, _Ty2>&& _Pr) noexcept {
    // get const rvalue reference to element _Ty2 in pair _Pr
    return _STD forward<const _Ty2>(_Pr.second);
}

_EXPORT_STD template <class _Ty, class _Other = _Ty>
_CONSTEXPR20 _Ty exchange(_Ty& _Val, _Other&& _New_val)
    noexcept(conjunction_v<is_nothrow_move_constructible<_Ty>, is_nothrow_assignable<_Ty&, _Other>>) {
    // assign _New_val to _Val, return previous _Val
    _Ty _Old_val = static_cast<_Ty&&>(_Val);
    _Val         = static_cast<_Other&&>(_New_val);
    return _Old_val;
}

_EXPORT_STD template <class _Ty>
_NODISCARD _MSVC_INTRINSIC constexpr add_const_t<_Ty>& as_const(_Ty& _Val) noexcept { // view _Val through const lenses
    return _Val;
}

_EXPORT_STD template <class _Ty>
void as_const(const _Ty&&) = delete;

#if _HAS_CXX17
_EXPORT_STD struct in_place_t { // tag used to select a constructor which initializes a contained object in place
    explicit in_place_t() = default;
};
_EXPORT_STD inline constexpr in_place_t in_place{};

_EXPORT_STD template <class>
struct in_place_type_t { // tag that selects a type to construct in place
    explicit in_place_type_t() = default;
};
_EXPORT_STD template <class _Ty>
constexpr in_place_type_t<_Ty> in_place_type{};

_EXPORT_STD template <size_t>
struct in_place_index_t { // tag that selects the index of a type to construct in place
    explicit in_place_index_t() = default;
};
_EXPORT_STD template <size_t _Idx>
constexpr in_place_index_t<_Idx> in_place_index{};
#endif // _HAS_CXX17

template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool _Cmp_equal(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    _STL_INTERNAL_STATIC_ASSERT(_Is_nonbool_integral<_Ty1> && _Is_nonbool_integral<_Ty2>); // allows character types
    if constexpr (is_signed_v<_Ty1> == is_signed_v<_Ty2>) {
        return _Left == _Right;
    } else if constexpr (is_signed_v<_Ty2>) {
        return _Left == static_cast<make_unsigned_t<_Ty2>>(_Right) && _Right >= 0;
    } else {
        return static_cast<make_unsigned_t<_Ty1>>(_Left) == _Right && _Left >= 0;
    }
}

template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool _Cmp_not_equal(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    return !_STD _Cmp_equal(_Left, _Right);
}

template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool _Cmp_less(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    _STL_INTERNAL_STATIC_ASSERT(_Is_nonbool_integral<_Ty1> && _Is_nonbool_integral<_Ty2>); // allows character types
    if constexpr (is_signed_v<_Ty1> == is_signed_v<_Ty2>) {
        return _Left < _Right;
    } else if constexpr (is_signed_v<_Ty2>) {
        return _Right > 0 && _Left < static_cast<make_unsigned_t<_Ty2>>(_Right);
    } else {
        return _Left < 0 || static_cast<make_unsigned_t<_Ty1>>(_Left) < _Right;
    }
}

template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool _Cmp_greater(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    return _STD _Cmp_less(_Right, _Left);
}

template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool _Cmp_less_equal(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    return !_STD _Cmp_less(_Right, _Left);
}

template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool _Cmp_greater_equal(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    return !_STD _Cmp_less(_Left, _Right);
}

template <class _Ty>
_NODISCARD constexpr _Ty _Min_limit() noexcept { // same as (numeric_limits<_Ty>::min)(), less throughput cost
    _STL_INTERNAL_STATIC_ASSERT(is_integral_v<_Ty>); // doesn't attempt to handle all types
    if constexpr (is_signed_v<_Ty>) {
        constexpr auto _Unsigned_max = static_cast<make_unsigned_t<_Ty>>(-1);
        return static_cast<_Ty>((_Unsigned_max >> 1) + 1); // well-defined, N4950 [conv.integral]/3
    } else {
        return 0;
    }
}

template <class _Ty>
_NODISCARD constexpr _Ty _Max_limit() noexcept { // same as (numeric_limits<_Ty>::max)(), less throughput cost
    _STL_INTERNAL_STATIC_ASSERT(is_integral_v<_Ty>); // doesn't attempt to handle all types
    if constexpr (is_signed_v<_Ty>) {
        constexpr auto _Unsigned_max = static_cast<make_unsigned_t<_Ty>>(-1);
        return static_cast<_Ty>(_Unsigned_max >> 1);
    } else {
        return static_cast<_Ty>(-1);
    }
}

template <class _Rx, class _Ty>
_NODISCARD constexpr bool _In_range(const _Ty _Value) noexcept {
    _STL_INTERNAL_STATIC_ASSERT(_Is_nonbool_integral<_Rx> && _Is_nonbool_integral<_Ty>); // allows character types

    constexpr auto _Ty_min = _Min_limit<_Ty>();
    constexpr auto _Rx_min = _Min_limit<_Rx>();

    if constexpr (_STD _Cmp_less(_Ty_min, _Rx_min)) {
        if (_Value < _Ty{_Rx_min}) {
            return false;
        }
    }

    constexpr auto _Ty_max = _Max_limit<_Ty>();
    constexpr auto _Rx_max = _Max_limit<_Rx>();

    if constexpr (_STD _Cmp_greater(_Ty_max, _Rx_max)) {
        if (_Value > _Ty{_Rx_max}) {
            return false;
        }
    }

    return true;
}

#if _HAS_CXX20
template <class _Ty>
constexpr bool _Is_standard_integer = _Is_any_of_v<remove_cv_t<_Ty>, signed char, short, int, long, long long,
    unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long>;

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool cmp_equal(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    static_assert(_Is_standard_integer<_Ty1> && _Is_standard_integer<_Ty2>,
        "The integer comparison functions only accept standard and extended integer types.");
    return _STD _Cmp_equal(_Left, _Right);
}

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool cmp_not_equal(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    static_assert(_Is_standard_integer<_Ty1> && _Is_standard_integer<_Ty2>,
        "The integer comparison functions only accept standard and extended integer types.");
    return _STD _Cmp_not_equal(_Left, _Right);
}

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool cmp_less(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    static_assert(_Is_standard_integer<_Ty1> && _Is_standard_integer<_Ty2>,
        "The integer comparison functions only accept standard and extended integer types.");
    return _STD _Cmp_less(_Left, _Right);
}

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool cmp_greater(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    static_assert(_Is_standard_integer<_Ty1> && _Is_standard_integer<_Ty2>,
        "The integer comparison functions only accept standard and extended integer types.");
    return _STD _Cmp_greater(_Left, _Right);
}

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool cmp_less_equal(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    static_assert(_Is_standard_integer<_Ty1> && _Is_standard_integer<_Ty2>,
        "The integer comparison functions only accept standard and extended integer types.");
    return _STD _Cmp_less_equal(_Left, _Right);
}

_EXPORT_STD template <class _Ty1, class _Ty2>
_NODISCARD constexpr bool cmp_greater_equal(const _Ty1 _Left, const _Ty2 _Right) noexcept {
    static_assert(_Is_standard_integer<_Ty1> && _Is_standard_integer<_Ty2>,
        "The integer comparison functions only accept standard and extended integer types.");
    return _STD _Cmp_greater_equal(_Left, _Right);
}

_EXPORT_STD template <class _Rx, class _Ty>
_NODISCARD constexpr bool in_range(const _Ty _Value) noexcept {
    static_assert(_Is_standard_integer<_Rx> && _Is_standard_integer<_Ty>,
        "The integer comparison functions only accept standard and extended integer types.");
    return _STD _In_range<_Rx>(_Value);
}
#endif // _HAS_CXX20

#if _HAS_CXX23
_EXPORT_STD template <class _Ty>
_NODISCARD _MSVC_INTRINSIC constexpr underlying_type_t<_Ty> to_underlying(_Ty _Value) noexcept {
    return static_cast<underlying_type_t<_Ty>>(_Value);
}

_EXPORT_STD [[noreturn]] __forceinline void unreachable() noexcept /* strengthened */ {
    _STL_UNREACHABLE;
#ifdef _DEBUG
    _CSTD abort(); // likely to be called in debug mode, but can't be relied upon - already entered the UB territory
#endif // defined(_DEBUG)
}

template <class _Ty, class _Uty,
    class _Tmp = _Maybe_const<is_const_v<remove_reference_t<_Ty>>, remove_reference_t<_Uty>>>
using _Forward_like_t = conditional_t<is_rvalue_reference_v<_Ty&&>, _Tmp&&, _Tmp&>;

_EXPORT_STD template <class _Ty, class _Uty>
_NODISCARD _MSVC_INTRINSIC constexpr _Forward_like_t<_Ty, _Uty> forward_like(_Uty&& _Ux) noexcept {
    return static_cast<_Forward_like_t<_Ty, _Uty>>(_Ux);
}
#endif // _HAS_CXX23

#if _HAS_TR1_NAMESPACE
namespace _DEPRECATE_TR1_NAMESPACE tr1 {
    using _STD get;
    using _STD tuple_element;
    using _STD tuple_size;
} // namespace _DEPRECATE_TR1_NAMESPACE tr1
#endif // _HAS_TR1_NAMESPACE

_STD_END

// TRANSITION, non-_Ugly attribute tokens
#pragma pop_macro("lifetimebound")
#pragma pop_macro("known_semantics")
#pragma pop_macro("intrinsic")
#pragma pop_macro("msvc")

#pragma pop_macro("new")
_STL_RESTORE_CLANG_WARNINGS
#pragma warning(pop)
#pragma pack(pop)
#endif // _STL_COMPILER_PREPROCESSOR
#endif // _UTILITY_