Import stripped Arm GNU Toolchain 13.2.Rel1HEADumineko

https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads

Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c

1 files changed, 2349 insertions, 0 deletions

diff --git a/aarch64-none-linux-gnu/include/c++/13.2.1/tuple b/aarch64-none-linux-gnu/include/c++/13.2.1/tuple
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@@ -0,0 +1,2349 @@
+// <tuple> -*- C++ -*-
+
+// Copyright (C) 2007-2023 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library 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; either version 3, or (at your option)
+// any later version.
+
+// This library 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.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file include/tuple
+ *  This is a Standard C++ Library header.
+ */
+
+#ifndef _GLIBCXX_TUPLE
+#define _GLIBCXX_TUPLE 1
+
+#pragma GCC system_header
+
+#if __cplusplus < 201103L
+# include <bits/c++0x_warning.h>
+#else
+
+#include <bits/stl_pair.h>		// for std::pair
+#include <bits/uses_allocator.h>	// for std::allocator_arg_t
+#include <bits/utility.h>		// for std::tuple_size etc.
+#include <bits/invoke.h>		// for std::__invoke
+#if __cplusplus > 201703L
+# include <compare>
+# include <bits/ranges_util.h>		// for std::ranges::subrange
+# define __cpp_lib_constexpr_tuple 201811L
+#endif
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+  /**
+   *  @addtogroup utilities
+   *  @{
+   */
+
+  template<typename... _Elements>
+    class tuple;
+
+  template<typename _Tp>
+    struct __is_empty_non_tuple : is_empty<_Tp> { };
+
+  // Using EBO for elements that are tuples causes ambiguous base errors.
+  template<typename _El0, typename... _El>
+    struct __is_empty_non_tuple<tuple<_El0, _El...>> : false_type { };
+
+  // Use the Empty Base-class Optimization for empty, non-final types.
+  template<typename _Tp>
+    using __empty_not_final
+    = __conditional_t<__is_final(_Tp), false_type,
+		      __is_empty_non_tuple<_Tp>>;
+
+  template<size_t _Idx, typename _Head,
+	   bool = __empty_not_final<_Head>::value>
+    struct _Head_base;
+
+#if __has_cpp_attribute(__no_unique_address__)
+  template<size_t _Idx, typename _Head>
+    struct _Head_base<_Idx, _Head, true>
+    {
+      constexpr _Head_base()
+      : _M_head_impl() { }
+
+      constexpr _Head_base(const _Head& __h)
+      : _M_head_impl(__h) { }
+
+      constexpr _Head_base(const _Head_base&) = default;
+      constexpr _Head_base(_Head_base&&) = default;
+
+      template<typename _UHead>
+	constexpr _Head_base(_UHead&& __h)
+	: _M_head_impl(std::forward<_UHead>(__h)) { }
+
+      _GLIBCXX20_CONSTEXPR
+      _Head_base(allocator_arg_t, __uses_alloc0)
+      : _M_head_impl() { }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(allocator_arg_t, __uses_alloc1<_Alloc> __a)
+	: _M_head_impl(allocator_arg, *__a._M_a) { }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(allocator_arg_t, __uses_alloc2<_Alloc> __a)
+	: _M_head_impl(*__a._M_a) { }
+
+      template<typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(__uses_alloc0, _UHead&& __uhead)
+	: _M_head_impl(std::forward<_UHead>(__uhead)) { }
+
+      template<typename _Alloc, typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
+	: _M_head_impl(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead))
+	{ }
+
+      template<typename _Alloc, typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
+	: _M_head_impl(std::forward<_UHead>(__uhead), *__a._M_a) { }
+
+      static constexpr _Head&
+      _M_head(_Head_base& __b) noexcept { return __b._M_head_impl; }
+
+      static constexpr const _Head&
+      _M_head(const _Head_base& __b) noexcept { return __b._M_head_impl; }
+
+      [[__no_unique_address__]] _Head _M_head_impl;
+    };
+#else
+  template<size_t _Idx, typename _Head>
+    struct _Head_base<_Idx, _Head, true>
+    : public _Head
+    {
+      constexpr _Head_base()
+      : _Head() { }
+
+      constexpr _Head_base(const _Head& __h)
+      : _Head(__h) { }
+
+      constexpr _Head_base(const _Head_base&) = default;
+      constexpr _Head_base(_Head_base&&) = default;
+
+      template<typename _UHead>
+        constexpr _Head_base(_UHead&& __h)
+	: _Head(std::forward<_UHead>(__h)) { }
+
+      _GLIBCXX20_CONSTEXPR
+      _Head_base(allocator_arg_t, __uses_alloc0)
+      : _Head() { }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(allocator_arg_t, __uses_alloc1<_Alloc> __a)
+	: _Head(allocator_arg, *__a._M_a) { }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(allocator_arg_t, __uses_alloc2<_Alloc> __a)
+	: _Head(*__a._M_a) { }
+
+      template<typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(__uses_alloc0, _UHead&& __uhead)
+	: _Head(std::forward<_UHead>(__uhead)) { }
+
+      template<typename _Alloc, typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
+	: _Head(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead)) { }
+
+      template<typename _Alloc, typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
+	: _Head(std::forward<_UHead>(__uhead), *__a._M_a) { }
+
+      static constexpr _Head&
+      _M_head(_Head_base& __b) noexcept { return __b; }
+
+      static constexpr const _Head&
+      _M_head(const _Head_base& __b) noexcept { return __b; }
+    };
+#endif
+
+  template<size_t _Idx, typename _Head>
+    struct _Head_base<_Idx, _Head, false>
+    {
+      constexpr _Head_base()
+      : _M_head_impl() { }
+
+      constexpr _Head_base(const _Head& __h)
+      : _M_head_impl(__h) { }
+
+      constexpr _Head_base(const _Head_base&) = default;
+      constexpr _Head_base(_Head_base&&) = default;
+
+      template<typename _UHead>
+        constexpr _Head_base(_UHead&& __h)
+	: _M_head_impl(std::forward<_UHead>(__h)) { }
+
+      _GLIBCXX20_CONSTEXPR
+      _Head_base(allocator_arg_t, __uses_alloc0)
+      : _M_head_impl() { }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(allocator_arg_t, __uses_alloc1<_Alloc> __a)
+	: _M_head_impl(allocator_arg, *__a._M_a) { }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(allocator_arg_t, __uses_alloc2<_Alloc> __a)
+	: _M_head_impl(*__a._M_a) { }
+
+      template<typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(__uses_alloc0, _UHead&& __uhead)
+	: _M_head_impl(std::forward<_UHead>(__uhead)) { }
+
+      template<typename _Alloc, typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
+	: _M_head_impl(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead))
+	{ }
+
+      template<typename _Alloc, typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
+	: _M_head_impl(std::forward<_UHead>(__uhead), *__a._M_a) { }
+
+      static constexpr _Head&
+      _M_head(_Head_base& __b) noexcept { return __b._M_head_impl; }
+
+      static constexpr const _Head&
+      _M_head(const _Head_base& __b) noexcept { return __b._M_head_impl; }
+
+      _Head _M_head_impl;
+    };
+
+  /**
+   * Contains the actual implementation of the @c tuple template, stored
+   * as a recursive inheritance hierarchy from the first element (most
+   * derived class) to the last (least derived class). The @c Idx
+   * parameter gives the 0-based index of the element stored at this
+   * point in the hierarchy; we use it to implement a constant-time
+   * get() operation.
+   */
+  template<size_t _Idx, typename... _Elements>
+    struct _Tuple_impl;
+
+  /**
+   * Recursive tuple implementation. Here we store the @c Head element
+   * and derive from a @c Tuple_impl containing the remaining elements
+   * (which contains the @c Tail).
+   */
+  template<size_t _Idx, typename _Head, typename... _Tail>
+    struct _Tuple_impl<_Idx, _Head, _Tail...>
+    : public _Tuple_impl<_Idx + 1, _Tail...>,
+      private _Head_base<_Idx, _Head>
+    {
+      template<size_t, typename...> friend struct _Tuple_impl;
+
+      typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
+      typedef _Head_base<_Idx, _Head> _Base;
+
+      static constexpr _Head&
+      _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
+
+      static constexpr const _Head&
+      _M_head(const _Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
+
+      static constexpr _Inherited&
+      _M_tail(_Tuple_impl& __t) noexcept { return __t; }
+
+      static constexpr const _Inherited&
+      _M_tail(const _Tuple_impl& __t) noexcept { return __t; }
+
+      constexpr _Tuple_impl()
+      : _Inherited(), _Base() { }
+
+      explicit constexpr
+      _Tuple_impl(const _Head& __head, const _Tail&... __tail)
+      : _Inherited(__tail...), _Base(__head)
+      { }
+
+      template<typename _UHead, typename... _UTail,
+	       typename = __enable_if_t<sizeof...(_Tail) == sizeof...(_UTail)>>
+	explicit constexpr
+	_Tuple_impl(_UHead&& __head, _UTail&&... __tail)
+	: _Inherited(std::forward<_UTail>(__tail)...),
+	  _Base(std::forward<_UHead>(__head))
+	{ }
+
+      constexpr _Tuple_impl(const _Tuple_impl&) = default;
+
+      // _GLIBCXX_RESOLVE_LIB_DEFECTS
+      // 2729. Missing SFINAE on std::pair::operator=
+      _Tuple_impl& operator=(const _Tuple_impl&) = delete;
+
+      _Tuple_impl(_Tuple_impl&&) = default;
+
+      template<typename... _UElements>
+	constexpr
+	_Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)
+	: _Inherited(_Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
+	  _Base(_Tuple_impl<_Idx, _UElements...>::_M_head(__in))
+	{ }
+
+      template<typename _UHead, typename... _UTails>
+	constexpr
+	_Tuple_impl(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
+	: _Inherited(std::move
+		     (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
+	  _Base(std::forward<_UHead>
+		(_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in)))
+	{ }
+
+#if __cplusplus > 202002L
+      template<typename... _UElements>
+	constexpr
+	_Tuple_impl(_Tuple_impl<_Idx, _UElements...>& __in)
+	: _Inherited(_Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
+	  _Base(_Tuple_impl<_Idx, _UElements...>::_M_head(__in))
+	{ }
+
+      template<typename _UHead, typename... _UTails>
+	constexpr
+	_Tuple_impl(const _Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
+	: _Inherited(std::move
+		     (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
+	  _Base(std::forward<const _UHead>
+		(_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in)))
+	{ }
+#endif // C++23
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a)
+	: _Inherited(__tag, __a),
+	  _Base(__tag, __use_alloc<_Head>(__a))
+	{ }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    const _Head& __head, const _Tail&... __tail)
+	: _Inherited(__tag, __a, __tail...),
+	  _Base(__use_alloc<_Head, _Alloc, _Head>(__a), __head)
+	{ }
+
+      template<typename _Alloc, typename _UHead, typename... _UTail,
+	       typename = __enable_if_t<sizeof...(_Tail) == sizeof...(_UTail)>>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    _UHead&& __head, _UTail&&... __tail)
+	: _Inherited(__tag, __a, std::forward<_UTail>(__tail)...),
+	  _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
+		std::forward<_UHead>(__head))
+	{ }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    const _Tuple_impl& __in)
+	: _Inherited(__tag, __a, _M_tail(__in)),
+	  _Base(__use_alloc<_Head, _Alloc, _Head>(__a), _M_head(__in))
+	{ }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    _Tuple_impl&& __in)
+	: _Inherited(__tag, __a, std::move(_M_tail(__in))),
+	  _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
+		std::forward<_Head>(_M_head(__in)))
+	{ }
+
+      template<typename _Alloc, typename _UHead, typename... _UTails>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    const _Tuple_impl<_Idx, _UHead, _UTails...>& __in)
+	: _Inherited(__tag, __a,
+		     _Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in)),
+	  _Base(__use_alloc<_Head, _Alloc, const _UHead&>(__a),
+		_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))
+	{ }
+
+      template<typename _Alloc, typename _UHead, typename... _UTails>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    _Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
+	: _Inherited(__tag, __a, std::move
+		     (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
+	  _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
+		std::forward<_UHead>
+		(_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in)))
+	{ }
+
+#if __cplusplus > 202002L
+      template<typename _Alloc, typename _UHead, typename... _UTails>
+	constexpr
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    _Tuple_impl<_Idx, _UHead, _UTails...>& __in)
+	: _Inherited(__tag, __a,
+		     _Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in)),
+	  _Base(__use_alloc<_Head, _Alloc, _UHead&>(__a),
+		_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))
+	{ }
+
+      template<typename _Alloc, typename _UHead, typename... _UTails>
+	constexpr
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    const _Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
+	: _Inherited(__tag, __a, std::move
+		     (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
+	  _Base(__use_alloc<_Head, _Alloc, const _UHead>(__a),
+		std::forward<const _UHead>
+		(_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in)))
+	{ }
+#endif // C++23
+
+      template<typename... _UElements>
+	_GLIBCXX20_CONSTEXPR
+	void
+	_M_assign(const _Tuple_impl<_Idx, _UElements...>& __in)
+	{
+	  _M_head(*this) = _Tuple_impl<_Idx, _UElements...>::_M_head(__in);
+	  _M_tail(*this)._M_assign(
+	      _Tuple_impl<_Idx, _UElements...>::_M_tail(__in));
+	}
+
+      template<typename _UHead, typename... _UTails>
+	_GLIBCXX20_CONSTEXPR
+	void
+	_M_assign(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
+	{
+	  _M_head(*this) = std::forward<_UHead>
+	    (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in));
+	  _M_tail(*this)._M_assign(
+	      std::move(_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in)));
+	}
+
+#if __cplusplus > 202002L
+      template<typename... _UElements>
+	constexpr void
+	_M_assign(const _Tuple_impl<_Idx, _UElements...>& __in) const
+	{
+	  _M_head(*this) = _Tuple_impl<_Idx, _UElements...>::_M_head(__in);
+	  _M_tail(*this)._M_assign(
+	      _Tuple_impl<_Idx, _UElements...>::_M_tail(__in));
+	}
+
+      template<typename _UHead, typename... _UTails>
+	constexpr void
+	_M_assign(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in) const
+	{
+	  _M_head(*this) = std::forward<_UHead>
+	    (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in));
+	  _M_tail(*this)._M_assign(
+	      std::move(_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in)));
+	}
+#endif // C++23
+
+    protected:
+      _GLIBCXX20_CONSTEXPR
+      void
+      _M_swap(_Tuple_impl& __in)
+      {
+	using std::swap;
+	swap(_M_head(*this), _M_head(__in));
+	_Inherited::_M_swap(_M_tail(__in));
+      }
+
+#if __cplusplus > 202002L
+      constexpr void
+      _M_swap(const _Tuple_impl& __in) const
+      {
+	using std::swap;
+	swap(_M_head(*this), _M_head(__in));
+	_Inherited::_M_swap(_M_tail(__in));
+      }
+#endif // C++23
+    };
+
+  // Basis case of inheritance recursion.
+  template<size_t _Idx, typename _Head>
+    struct _Tuple_impl<_Idx, _Head>
+    : private _Head_base<_Idx, _Head>
+    {
+      template<size_t, typename...> friend struct _Tuple_impl;
+
+      typedef _Head_base<_Idx, _Head> _Base;
+
+      static constexpr _Head&
+      _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
+
+      static constexpr const _Head&
+      _M_head(const _Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
+
+      constexpr
+      _Tuple_impl()
+      : _Base() { }
+
+      explicit constexpr
+      _Tuple_impl(const _Head& __head)
+      : _Base(__head)
+      { }
+
+      template<typename _UHead>
+	explicit constexpr
+	_Tuple_impl(_UHead&& __head)
+	: _Base(std::forward<_UHead>(__head))
+	{ }
+
+      constexpr _Tuple_impl(const _Tuple_impl&) = default;
+
+      // _GLIBCXX_RESOLVE_LIB_DEFECTS
+      // 2729. Missing SFINAE on std::pair::operator=
+      _Tuple_impl& operator=(const _Tuple_impl&) = delete;
+
+#if _GLIBCXX_INLINE_VERSION
+      _Tuple_impl(_Tuple_impl&&) = default;
+#else
+      constexpr
+      _Tuple_impl(_Tuple_impl&& __in)
+      noexcept(is_nothrow_move_constructible<_Head>::value)
+      : _Base(static_cast<_Base&&>(__in))
+      { }
+#endif
+
+      template<typename _UHead>
+	constexpr
+	_Tuple_impl(const _Tuple_impl<_Idx, _UHead>& __in)
+	: _Base(_Tuple_impl<_Idx, _UHead>::_M_head(__in))
+	{ }
+
+      template<typename _UHead>
+	constexpr
+	_Tuple_impl(_Tuple_impl<_Idx, _UHead>&& __in)
+	: _Base(std::forward<_UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in)))
+	{ }
+
+#if __cplusplus > 202002L
+      template<typename _UHead>
+	constexpr
+	_Tuple_impl(_Tuple_impl<_Idx, _UHead>& __in)
+	: _Base(_Tuple_impl<_Idx, _UHead>::_M_head(__in))
+	{ }
+
+      template<typename _UHead>
+	constexpr
+	_Tuple_impl(const _Tuple_impl<_Idx, _UHead>&& __in)
+	: _Base(std::forward<const _UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in)))
+	{ }
+#endif // C++23
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a)
+	: _Base(__tag, __use_alloc<_Head>(__a))
+	{ }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    const _Head& __head)
+	: _Base(__use_alloc<_Head, _Alloc, const _Head&>(__a), __head)
+	{ }
+
+      template<typename _Alloc, typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    _UHead&& __head)
+	: _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
+		std::forward<_UHead>(__head))
+	{ }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    const _Tuple_impl& __in)
+	: _Base(__use_alloc<_Head, _Alloc, const _Head&>(__a), _M_head(__in))
+	{ }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    _Tuple_impl&& __in)
+	: _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
+		std::forward<_Head>(_M_head(__in)))
+	{ }
+
+      template<typename _Alloc, typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    const _Tuple_impl<_Idx, _UHead>& __in)
+	: _Base(__use_alloc<_Head, _Alloc, const _UHead&>(__a),
+		_Tuple_impl<_Idx, _UHead>::_M_head(__in))
+	{ }
+
+      template<typename _Alloc, typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    _Tuple_impl<_Idx, _UHead>&& __in)
+	: _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
+		std::forward<_UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in)))
+	{ }
+
+#if __cplusplus > 202002L
+      template<typename _Alloc, typename _UHead>
+	constexpr
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    _Tuple_impl<_Idx, _UHead>& __in)
+	: _Base(__use_alloc<_Head, _Alloc, _UHead&>(__a),
+		_Tuple_impl<_Idx, _UHead>::_M_head(__in))
+	{ }
+
+      template<typename _Alloc, typename _UHead>
+	constexpr
+	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
+		    const _Tuple_impl<_Idx, _UHead>&& __in)
+	: _Base(__use_alloc<_Head, _Alloc, const _UHead>(__a),
+		std::forward<const _UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in)))
+	{ }
+#endif // C++23
+
+      template<typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	void
+	_M_assign(const _Tuple_impl<_Idx, _UHead>& __in)
+	{
+	  _M_head(*this) = _Tuple_impl<_Idx, _UHead>::_M_head(__in);
+	}
+
+      template<typename _UHead>
+	_GLIBCXX20_CONSTEXPR
+	void
+	_M_assign(_Tuple_impl<_Idx, _UHead>&& __in)
+	{
+	  _M_head(*this)
+	    = std::forward<_UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in));
+	}
+
+#if __cplusplus > 202002L
+      template<typename _UHead>
+	constexpr void
+	_M_assign(const _Tuple_impl<_Idx, _UHead>& __in) const
+	{
+	  _M_head(*this) = _Tuple_impl<_Idx, _UHead>::_M_head(__in);
+	}
+
+      template<typename _UHead>
+	constexpr void
+	_M_assign(_Tuple_impl<_Idx, _UHead>&& __in) const
+	{
+	  _M_head(*this)
+	    = std::forward<_UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in));
+	}
+#endif // C++23
+
+    protected:
+      _GLIBCXX20_CONSTEXPR
+      void
+      _M_swap(_Tuple_impl& __in)
+      {
+	using std::swap;
+	swap(_M_head(*this), _M_head(__in));
+      }
+
+#if __cplusplus > 202002L
+      constexpr void
+      _M_swap(const _Tuple_impl& __in) const
+      {
+	using std::swap;
+	swap(_M_head(*this), _M_head(__in));
+      }
+#endif // C++23
+    };
+
+  // Concept utility functions, reused in conditionally-explicit
+  // constructors.
+  template<bool, typename... _Types>
+    struct _TupleConstraints
+    {
+      template<typename... _UTypes>
+	using __constructible = __and_<is_constructible<_Types, _UTypes>...>;
+
+      template<typename... _UTypes>
+	using __convertible = __and_<is_convertible<_UTypes, _Types>...>;
+
+      // Constraint for a non-explicit constructor.
+      // True iff each Ti in _Types... can be constructed from Ui in _UTypes...
+      // and every Ui is implicitly convertible to Ti.
+      template<typename... _UTypes>
+	static constexpr bool __is_implicitly_constructible()
+	{
+	  return __and_<__constructible<_UTypes...>,
+			__convertible<_UTypes...>
+			>::value;
+	}
+
+      // Constraint for a non-explicit constructor.
+      // True iff each Ti in _Types... can be constructed from Ui in _UTypes...
+      // but not every Ui is implicitly convertible to Ti.
+      template<typename... _UTypes>
+	static constexpr bool __is_explicitly_constructible()
+	{
+	  return __and_<__constructible<_UTypes...>,
+			__not_<__convertible<_UTypes...>>
+			>::value;
+	}
+
+      static constexpr bool __is_implicitly_default_constructible()
+      {
+	return __and_<std::__is_implicitly_default_constructible<_Types>...
+		      >::value;
+      }
+
+      static constexpr bool __is_explicitly_default_constructible()
+      {
+	return __and_<is_default_constructible<_Types>...,
+		      __not_<__and_<
+			std::__is_implicitly_default_constructible<_Types>...>
+		      >>::value;
+      }
+    };
+
+  // Partial specialization used when a required precondition isn't met,
+  // e.g. when sizeof...(_Types) != sizeof...(_UTypes).
+  template<typename... _Types>
+    struct _TupleConstraints<false, _Types...>
+    {
+      template<typename... _UTypes>
+	static constexpr bool __is_implicitly_constructible()
+	{ return false; }
+
+      template<typename... _UTypes>
+	static constexpr bool __is_explicitly_constructible()
+	{ return false; }
+    };
+
+  /// Primary class template, tuple
+  template<typename... _Elements>
+    class tuple : public _Tuple_impl<0, _Elements...>
+    {
+      typedef _Tuple_impl<0, _Elements...> _Inherited;
+
+      template<bool _Cond>
+	using _TCC = _TupleConstraints<_Cond, _Elements...>;
+
+      // Constraint for non-explicit default constructor
+      template<bool _Dummy>
+	using _ImplicitDefaultCtor = __enable_if_t<
+	  _TCC<_Dummy>::__is_implicitly_default_constructible(),
+	  bool>;
+
+      // Constraint for explicit default constructor
+      template<bool _Dummy>
+	using _ExplicitDefaultCtor = __enable_if_t<
+	  _TCC<_Dummy>::__is_explicitly_default_constructible(),
+	  bool>;
+
+      // Constraint for non-explicit constructors
+      template<bool _Cond, typename... _Args>
+	using _ImplicitCtor = __enable_if_t<
+	  _TCC<_Cond>::template __is_implicitly_constructible<_Args...>(),
+	  bool>;
+
+      // Constraint for non-explicit constructors
+      template<bool _Cond, typename... _Args>
+	using _ExplicitCtor = __enable_if_t<
+	  _TCC<_Cond>::template __is_explicitly_constructible<_Args...>(),
+	  bool>;
+
+      template<typename... _UElements>
+	static constexpr
+	__enable_if_t<sizeof...(_UElements) == sizeof...(_Elements), bool>
+	__assignable()
+	{ return __and_<is_assignable<_Elements&, _UElements>...>::value; }
+
+      // Condition for noexcept-specifier of an assignment operator.
+      template<typename... _UElements>
+	static constexpr bool __nothrow_assignable()
+	{
+	  return
+	    __and_<is_nothrow_assignable<_Elements&, _UElements>...>::value;
+	}
+
+      // Condition for noexcept-specifier of a constructor.
+      template<typename... _UElements>
+	static constexpr bool __nothrow_constructible()
+	{
+	  return
+	    __and_<is_nothrow_constructible<_Elements, _UElements>...>::value;
+	}
+
+      // Constraint for tuple(_UTypes&&...) where sizeof...(_UTypes) == 1.
+      template<typename _Up>
+	static constexpr bool __valid_args()
+	{
+	  return sizeof...(_Elements) == 1
+	    && !is_same<tuple, __remove_cvref_t<_Up>>::value;
+	}
+
+      // Constraint for tuple(_UTypes&&...) where sizeof...(_UTypes) > 1.
+      template<typename, typename, typename... _Tail>
+	static constexpr bool __valid_args()
+	{ return (sizeof...(_Tail) + 2) == sizeof...(_Elements); }
+
+      /* Constraint for constructors with a tuple<UTypes...> parameter ensures
+       * that the constructor is only viable when it would not interfere with
+       * tuple(UTypes&&...) or tuple(const tuple&) or tuple(tuple&&).
+       * Such constructors are only viable if:
+       * either sizeof...(Types) != 1,
+       * or (when Types... expands to T and UTypes... expands to U)
+       * is_convertible_v<TUPLE, T>, is_constructible_v<T, TUPLE>,
+       * and is_same_v<T, U> are all false.
+       */
+      template<typename _Tuple, typename = tuple,
+	       typename = __remove_cvref_t<_Tuple>>
+	struct _UseOtherCtor
+	: false_type
+	{ };
+      // If TUPLE is convertible to the single element in *this,
+      // then TUPLE should match tuple(UTypes&&...) instead.
+      template<typename _Tuple, typename _Tp, typename _Up>
+	struct _UseOtherCtor<_Tuple, tuple<_Tp>, tuple<_Up>>
+	: __or_<is_convertible<_Tuple, _Tp>, is_constructible<_Tp, _Tuple>>::type
+	{ };
+      // If TUPLE and *this each have a single element of the same type,
+      // then TUPLE should match a copy/move constructor instead.
+      template<typename _Tuple, typename _Tp>
+	struct _UseOtherCtor<_Tuple, tuple<_Tp>, tuple<_Tp>>
+	: true_type
+	{ };
+
+      // Return true iff sizeof...(Types) == 1 && tuple_size_v<TUPLE> == 1
+      // and the single element in Types can be initialized from TUPLE,
+      // or is the same type as tuple_element_t<0, TUPLE>.
+      template<typename _Tuple>
+	static constexpr bool __use_other_ctor()
+	{ return _UseOtherCtor<_Tuple>::value; }
+
+#if __cplusplus > 202002L
+      template<typename... _Args>
+	static constexpr bool __constructible
+	  = _TCC<true>::template __constructible<_Args...>::value;
+
+      template<typename... _Args>
+	static constexpr bool __convertible
+	  = _TCC<true>::template __convertible<_Args...>::value;
+#endif // C++23
+
+    public:
+      template<typename _Dummy = void,
+	       _ImplicitDefaultCtor<is_void<_Dummy>::value> = true>
+	constexpr
+	tuple()
+	noexcept(__and_<is_nothrow_default_constructible<_Elements>...>::value)
+	: _Inherited() { }
+
+      template<typename _Dummy = void,
+	       _ExplicitDefaultCtor<is_void<_Dummy>::value> = false>
+	explicit constexpr
+	tuple()
+	noexcept(__and_<is_nothrow_default_constructible<_Elements>...>::value)
+	: _Inherited() { }
+
+      template<bool _NotEmpty = (sizeof...(_Elements) >= 1),
+	       _ImplicitCtor<_NotEmpty, const _Elements&...> = true>
+	constexpr
+	tuple(const _Elements&... __elements)
+	noexcept(__nothrow_constructible<const _Elements&...>())
+	: _Inherited(__elements...) { }
+
+      template<bool _NotEmpty = (sizeof...(_Elements) >= 1),
+	       _ExplicitCtor<_NotEmpty, const _Elements&...> = false>
+	explicit constexpr
+	tuple(const _Elements&... __elements)
+	noexcept(__nothrow_constructible<const _Elements&...>())
+	: _Inherited(__elements...) { }
+
+      template<typename... _UElements,
+	       bool _Valid = __valid_args<_UElements...>(),
+	       _ImplicitCtor<_Valid, _UElements...> = true>
+	constexpr
+	tuple(_UElements&&... __elements)
+	noexcept(__nothrow_constructible<_UElements...>())
+	: _Inherited(std::forward<_UElements>(__elements)...) { }
+
+      template<typename... _UElements,
+	       bool _Valid = __valid_args<_UElements...>(),
+	       _ExplicitCtor<_Valid, _UElements...> = false>
+	explicit constexpr
+	tuple(_UElements&&... __elements)
+	noexcept(__nothrow_constructible<_UElements...>())
+	: _Inherited(std::forward<_UElements>(__elements)...) {	}
+
+      constexpr tuple(const tuple&) = default;
+
+      constexpr tuple(tuple&&) = default;
+
+      template<typename... _UElements,
+	       bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
+			   && !__use_other_ctor<const tuple<_UElements...>&>(),
+	       _ImplicitCtor<_Valid, const _UElements&...> = true>
+	constexpr
+	tuple(const tuple<_UElements...>& __in)
+	noexcept(__nothrow_constructible<const _UElements&...>())
+	: _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
+	{ }
+
+      template<typename... _UElements,
+	       bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
+			   && !__use_other_ctor<const tuple<_UElements...>&>(),
+	       _ExplicitCtor<_Valid, const _UElements&...> = false>
+	explicit constexpr
+	tuple(const tuple<_UElements...>& __in)
+	noexcept(__nothrow_constructible<const _UElements&...>())
+	: _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
+	{ }
+
+      template<typename... _UElements,
+	       bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
+			     && !__use_other_ctor<tuple<_UElements...>&&>(),
+	       _ImplicitCtor<_Valid, _UElements...> = true>
+	constexpr
+	tuple(tuple<_UElements...>&& __in)
+	noexcept(__nothrow_constructible<_UElements...>())
+	: _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }
+
+      template<typename... _UElements,
+	       bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
+			     && !__use_other_ctor<tuple<_UElements...>&&>(),
+	       _ExplicitCtor<_Valid, _UElements...> = false>
+	explicit constexpr
+	tuple(tuple<_UElements...>&& __in)
+	noexcept(__nothrow_constructible<_UElements...>())
+	: _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }
+
+#if __cplusplus > 202002L
+      template<typename... _UElements>
+	requires (sizeof...(_Elements) == sizeof...(_UElements))
+	  && (!__use_other_ctor<tuple<_UElements...>&>())
+	  && __constructible<_UElements&...>
+	explicit(!__convertible<_UElements&...>)
+	constexpr
+	tuple(tuple<_UElements...>& __in)
+	noexcept(__nothrow_constructible<_UElements&...>())
+	: _Inherited(static_cast<_Tuple_impl<0, _UElements...>&>(__in))
+	{ }
+
+      template<typename... _UElements>
+	requires (sizeof...(_Elements) == sizeof...(_UElements))
+	  && (!__use_other_ctor<const tuple<_UElements...>&&>())
+	  && __constructible<const _UElements...>
+	explicit(!__convertible<const _UElements...>)
+	constexpr
+	tuple(const tuple<_UElements...>&& __in)
+	noexcept(__nothrow_constructible<const _UElements...>())
+	: _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&&>(__in)) { }
+#endif // C++23
+
+      // Allocator-extended constructors.
+
+      template<typename _Alloc,
+	       _ImplicitDefaultCtor<is_object<_Alloc>::value> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a)
+	: _Inherited(__tag, __a) { }
+
+      template<typename _Alloc, bool _NotEmpty = (sizeof...(_Elements) >= 1),
+	       _ImplicitCtor<_NotEmpty, const _Elements&...> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const _Elements&... __elements)
+	: _Inherited(__tag, __a, __elements...) { }
+
+      template<typename _Alloc, bool _NotEmpty = (sizeof...(_Elements) >= 1),
+	       _ExplicitCtor<_NotEmpty, const _Elements&...> = false>
+	_GLIBCXX20_CONSTEXPR
+	explicit
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const _Elements&... __elements)
+	: _Inherited(__tag, __a, __elements...) { }
+
+      template<typename _Alloc, typename... _UElements,
+	       bool _Valid = __valid_args<_UElements...>(),
+	       _ImplicitCtor<_Valid, _UElements...> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      _UElements&&... __elements)
+	: _Inherited(__tag, __a, std::forward<_UElements>(__elements)...)
+	{ }
+
+      template<typename _Alloc, typename... _UElements,
+		 bool _Valid = __valid_args<_UElements...>(),
+	       _ExplicitCtor<_Valid, _UElements...> = false>
+	_GLIBCXX20_CONSTEXPR
+	explicit
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      _UElements&&... __elements)
+	: _Inherited(__tag, __a, std::forward<_UElements>(__elements)...)
+	{ }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
+	: _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
+	: _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
+
+      template<typename _Alloc, typename... _UElements,
+	       bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
+			     && !__use_other_ctor<const tuple<_UElements...>&>(),
+	       _ImplicitCtor<_Valid, const _UElements&...> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const tuple<_UElements...>& __in)
+	: _Inherited(__tag, __a,
+	             static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
+	{ }
+
+      template<typename _Alloc, typename... _UElements,
+	       bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
+			     && !__use_other_ctor<const tuple<_UElements...>&>(),
+	       _ExplicitCtor<_Valid, const _UElements&...> = false>
+	_GLIBCXX20_CONSTEXPR
+	explicit
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const tuple<_UElements...>& __in)
+	: _Inherited(__tag, __a,
+	             static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
+	{ }
+
+      template<typename _Alloc, typename... _UElements,
+	       bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
+			     && !__use_other_ctor<tuple<_UElements...>&&>(),
+	       _ImplicitCtor<_Valid, _UElements...> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      tuple<_UElements...>&& __in)
+	: _Inherited(__tag, __a,
+	             static_cast<_Tuple_impl<0, _UElements...>&&>(__in))
+	{ }
+
+      template<typename _Alloc, typename... _UElements,
+	       bool _Valid = (sizeof...(_Elements) == sizeof...(_UElements))
+			     && !__use_other_ctor<tuple<_UElements...>&&>(),
+	       _ExplicitCtor<_Valid, _UElements...> = false>
+	_GLIBCXX20_CONSTEXPR
+	explicit
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      tuple<_UElements...>&& __in)
+	: _Inherited(__tag, __a,
+	             static_cast<_Tuple_impl<0, _UElements...>&&>(__in))
+	{ }
+
+#if __cplusplus > 202002L
+      template<typename _Alloc, typename... _UElements>
+	requires (sizeof...(_Elements) == sizeof...(_UElements))
+	  && (!__use_other_ctor<tuple<_UElements...>&>())
+	  && __constructible<_UElements&...>
+	explicit(!__convertible<_UElements&...>)
+	constexpr
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      tuple<_UElements...>& __in)
+	: _Inherited(__tag, __a,
+	             static_cast<_Tuple_impl<0, _UElements...>&>(__in))
+	{ }
+
+      template<typename _Alloc, typename... _UElements>
+	requires (sizeof...(_Elements) == sizeof...(_UElements))
+	  && (!__use_other_ctor<const tuple<_UElements...>>())
+	  && __constructible<const _UElements...>
+	explicit(!__convertible<const _UElements...>)
+	constexpr
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const tuple<_UElements...>&& __in)
+	: _Inherited(__tag, __a,
+	             static_cast<const _Tuple_impl<0, _UElements...>&&>(__in))
+	{ }
+#endif // C++23
+
+      // tuple assignment
+
+      _GLIBCXX20_CONSTEXPR
+      tuple&
+      operator=(__conditional_t<__assignable<const _Elements&...>(),
+				const tuple&,
+				const __nonesuch&> __in)
+      noexcept(__nothrow_assignable<const _Elements&...>())
+      {
+	this->_M_assign(__in);
+	return *this;
+      }
+
+      _GLIBCXX20_CONSTEXPR
+      tuple&
+      operator=(__conditional_t<__assignable<_Elements...>(),
+				tuple&&,
+				__nonesuch&&> __in)
+      noexcept(__nothrow_assignable<_Elements...>())
+      {
+	this->_M_assign(std::move(__in));
+	return *this;
+      }
+
+      template<typename... _UElements>
+	_GLIBCXX20_CONSTEXPR
+	__enable_if_t<__assignable<const _UElements&...>(), tuple&>
+	operator=(const tuple<_UElements...>& __in)
+	noexcept(__nothrow_assignable<const _UElements&...>())
+	{
+	  this->_M_assign(__in);
+	  return *this;
+	}
+
+      template<typename... _UElements>
+	_GLIBCXX20_CONSTEXPR
+	__enable_if_t<__assignable<_UElements...>(), tuple&>
+	operator=(tuple<_UElements...>&& __in)
+	noexcept(__nothrow_assignable<_UElements...>())
+	{
+	  this->_M_assign(std::move(__in));
+	  return *this;
+	}
+
+#if __cplusplus > 202002L
+      constexpr const tuple&
+      operator=(const tuple& __in) const
+      requires (is_copy_assignable_v<const _Elements> && ...)
+      {
+	this->_M_assign(__in);
+	return *this;
+      }
+
+      constexpr const tuple&
+      operator=(tuple&& __in) const
+      requires (is_assignable_v<const _Elements&, _Elements> && ...)
+      {
+	this->_M_assign(std::move(__in));
+	return *this;
+      }
+
+      template<typename... _UElements>
+	constexpr const tuple&
+	operator=(const tuple<_UElements...>& __in) const
+	requires (sizeof...(_Elements) == sizeof...(_UElements))
+	  && (is_assignable_v<const _Elements&, const _UElements&> && ...)
+	{
+	  this->_M_assign(__in);
+	  return *this;
+	}
+
+      template<typename... _UElements>
+	constexpr const tuple&
+	operator=(tuple<_UElements...>&& __in) const
+	requires (sizeof...(_Elements) == sizeof...(_UElements))
+	  && (is_assignable_v<const _Elements&, _UElements> && ...)
+	{
+	  this->_M_assign(std::move(__in));
+	  return *this;
+	}
+#endif // C++23
+
+      // tuple swap
+      _GLIBCXX20_CONSTEXPR
+      void
+      swap(tuple& __in)
+      noexcept(__and_<__is_nothrow_swappable<_Elements>...>::value)
+      { _Inherited::_M_swap(__in); }
+
+#if __cplusplus > 202002L
+      // As an extension, we constrain the const swap member function in order
+      // to continue accepting explicit instantiation of tuples whose elements
+      // are not all const swappable.  Without this constraint, such an
+      // explicit instantiation would also instantiate the ill-formed body of
+      // this function and yield a hard error.  This constraint shouldn't
+      // affect the behavior of valid programs.
+      constexpr void
+      swap(const tuple& __in) const
+      noexcept(__and_v<__is_nothrow_swappable<const _Elements>...>)
+      requires (is_swappable_v<const _Elements> && ...)
+      { _Inherited::_M_swap(__in); }
+#endif // C++23
+    };
+
+#if __cpp_deduction_guides >= 201606
+  template<typename... _UTypes>
+    tuple(_UTypes...) -> tuple<_UTypes...>;
+  template<typename _T1, typename _T2>
+    tuple(pair<_T1, _T2>) -> tuple<_T1, _T2>;
+  template<typename _Alloc, typename... _UTypes>
+    tuple(allocator_arg_t, _Alloc, _UTypes...) -> tuple<_UTypes...>;
+  template<typename _Alloc, typename _T1, typename _T2>
+    tuple(allocator_arg_t, _Alloc, pair<_T1, _T2>) -> tuple<_T1, _T2>;
+  template<typename _Alloc, typename... _UTypes>
+    tuple(allocator_arg_t, _Alloc, tuple<_UTypes...>) -> tuple<_UTypes...>;
+#endif
+
+  // Explicit specialization, zero-element tuple.
+  template<>
+    class tuple<>
+    {
+    public:
+      _GLIBCXX20_CONSTEXPR
+      void swap(tuple&) noexcept { /* no-op */ }
+#if __cplusplus > 202002L
+      constexpr void swap(const tuple&) const noexcept { /* no-op */ }
+#endif
+      // We need the default since we're going to define no-op
+      // allocator constructors.
+      tuple() = default;
+      // No-op allocator constructors.
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t, const _Alloc&) noexcept { }
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t, const _Alloc&, const tuple&) noexcept { }
+    };
+
+  /// Partial specialization, 2-element tuple.
+  /// Includes construction and assignment from a pair.
+  template<typename _T1, typename _T2>
+    class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
+    {
+      typedef _Tuple_impl<0, _T1, _T2> _Inherited;
+
+      // Constraint for non-explicit default constructor
+      template<bool _Dummy, typename _U1, typename _U2>
+	using _ImplicitDefaultCtor = __enable_if_t<
+	  _TupleConstraints<_Dummy, _U1, _U2>::
+	    __is_implicitly_default_constructible(),
+	  bool>;
+
+      // Constraint for explicit default constructor
+      template<bool _Dummy, typename _U1, typename _U2>
+	using _ExplicitDefaultCtor = __enable_if_t<
+	  _TupleConstraints<_Dummy, _U1, _U2>::
+	    __is_explicitly_default_constructible(),
+	  bool>;
+
+      template<bool _Dummy>
+	using _TCC = _TupleConstraints<_Dummy, _T1, _T2>;
+
+      // Constraint for non-explicit constructors
+      template<bool _Cond, typename _U1, typename _U2>
+	using _ImplicitCtor = __enable_if_t<
+	  _TCC<_Cond>::template __is_implicitly_constructible<_U1, _U2>(),
+	  bool>;
+
+      // Constraint for non-explicit constructors
+      template<bool _Cond, typename _U1, typename _U2>
+	using _ExplicitCtor = __enable_if_t<
+	  _TCC<_Cond>::template __is_explicitly_constructible<_U1, _U2>(),
+	  bool>;
+
+      template<typename _U1, typename _U2>
+	static constexpr bool __assignable()
+	{
+	  return __and_<is_assignable<_T1&, _U1>,
+			is_assignable<_T2&, _U2>>::value;
+	}
+
+      template<typename _U1, typename _U2>
+	static constexpr bool __nothrow_assignable()
+	{
+	  return __and_<is_nothrow_assignable<_T1&, _U1>,
+			is_nothrow_assignable<_T2&, _U2>>::value;
+	}
+
+      template<typename _U1, typename _U2>
+	static constexpr bool __nothrow_constructible()
+	{
+	  return __and_<is_nothrow_constructible<_T1, _U1>,
+			    is_nothrow_constructible<_T2, _U2>>::value;
+	}
+
+      static constexpr bool __nothrow_default_constructible()
+      {
+	return __and_<is_nothrow_default_constructible<_T1>,
+		      is_nothrow_default_constructible<_T2>>::value;
+      }
+
+      template<typename _U1>
+	static constexpr bool __is_alloc_arg()
+	{ return is_same<__remove_cvref_t<_U1>, allocator_arg_t>::value; }
+
+#if __cplusplus > 202002L
+      template<typename _U1, typename _U2>
+	static constexpr bool __constructible
+	  = _TCC<true>::template __constructible<_U1, _U2>::value;
+
+      template<typename _U1, typename _U2>
+	static constexpr bool __convertible
+	  = _TCC<true>::template __convertible<_U1, _U2>::value;
+#endif // C++23
+
+    public:
+      template<bool _Dummy = true,
+	       _ImplicitDefaultCtor<_Dummy, _T1, _T2> = true>
+	constexpr
+	tuple()
+	noexcept(__nothrow_default_constructible())
+	: _Inherited() { }
+
+      template<bool _Dummy = true,
+	       _ExplicitDefaultCtor<_Dummy, _T1, _T2> = false>
+	explicit constexpr
+	tuple()
+	noexcept(__nothrow_default_constructible())
+	: _Inherited() { }
+
+      template<bool _Dummy = true,
+	       _ImplicitCtor<_Dummy, const _T1&, const _T2&> = true>
+	constexpr
+	tuple(const _T1& __a1, const _T2& __a2)
+	noexcept(__nothrow_constructible<const _T1&, const _T2&>())
+	: _Inherited(__a1, __a2) { }
+
+      template<bool _Dummy = true,
+	       _ExplicitCtor<_Dummy, const _T1&, const _T2&> = false>
+	explicit constexpr
+	tuple(const _T1& __a1, const _T2& __a2)
+	noexcept(__nothrow_constructible<const _T1&, const _T2&>())
+	: _Inherited(__a1, __a2) { }
+
+      template<typename _U1, typename _U2,
+	       _ImplicitCtor<!__is_alloc_arg<_U1>(), _U1, _U2> = true>
+	constexpr
+	tuple(_U1&& __a1, _U2&& __a2)
+	noexcept(__nothrow_constructible<_U1, _U2>())
+	: _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
+
+      template<typename _U1, typename _U2,
+	       _ExplicitCtor<!__is_alloc_arg<_U1>(), _U1, _U2> = false>
+	explicit constexpr
+	tuple(_U1&& __a1, _U2&& __a2)
+	noexcept(__nothrow_constructible<_U1, _U2>())
+	: _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
+
+      constexpr tuple(const tuple&) = default;
+
+      constexpr tuple(tuple&&) = default;
+
+      template<typename _U1, typename _U2,
+	       _ImplicitCtor<true, const _U1&, const _U2&> = true>
+	constexpr
+	tuple(const tuple<_U1, _U2>& __in)
+	noexcept(__nothrow_constructible<const _U1&, const _U2&>())
+	: _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
+
+      template<typename _U1, typename _U2,
+	       _ExplicitCtor<true, const _U1&, const _U2&> = false>
+	explicit constexpr
+	tuple(const tuple<_U1, _U2>& __in)
+	noexcept(__nothrow_constructible<const _U1&, const _U2&>())
+	: _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
+
+      template<typename _U1, typename _U2,
+	       _ImplicitCtor<true, _U1, _U2> = true>
+	constexpr
+	tuple(tuple<_U1, _U2>&& __in)
+	noexcept(__nothrow_constructible<_U1, _U2>())
+	: _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }
+
+      template<typename _U1, typename _U2,
+	       _ExplicitCtor<true, _U1, _U2> = false>
+	explicit constexpr
+	tuple(tuple<_U1, _U2>&& __in)
+	noexcept(__nothrow_constructible<_U1, _U2>())
+	: _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }
+
+#if __cplusplus > 202002L
+      template<typename _U1, typename _U2>
+	requires __constructible<_U1&, _U2&>
+	explicit(!__convertible<_U1&, _U2&>)
+	constexpr
+	tuple(tuple<_U1, _U2>& __in)
+	noexcept(__nothrow_constructible<_U1&, _U2&>())
+	: _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&>(__in)) { }
+
+      template<typename _U1, typename _U2>
+	requires __constructible<const _U1, const _U2>
+	explicit(!__convertible<const _U1, const _U2>)
+	constexpr
+	tuple(const tuple<_U1, _U2>&& __in)
+	noexcept(__nothrow_constructible<const _U1, const _U2>())
+	: _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&&>(__in)) { }
+#endif // C++23
+
+      template<typename _U1, typename _U2,
+	       _ImplicitCtor<true, const _U1&, const _U2&> = true>
+	constexpr
+	tuple(const pair<_U1, _U2>& __in)
+	noexcept(__nothrow_constructible<const _U1&, const _U2&>())
+	: _Inherited(__in.first, __in.second) { }
+
+      template<typename _U1, typename _U2,
+	       _ExplicitCtor<true, const _U1&, const _U2&> = false>
+	explicit constexpr
+	tuple(const pair<_U1, _U2>& __in)
+	noexcept(__nothrow_constructible<const _U1&, const _U2&>())
+	: _Inherited(__in.first, __in.second) { }
+
+      template<typename _U1, typename _U2,
+	       _ImplicitCtor<true, _U1, _U2> = true>
+	constexpr
+	tuple(pair<_U1, _U2>&& __in)
+	noexcept(__nothrow_constructible<_U1, _U2>())
+	: _Inherited(std::forward<_U1>(__in.first),
+		     std::forward<_U2>(__in.second)) { }
+
+      template<typename _U1, typename _U2,
+	       _ExplicitCtor<true, _U1, _U2> = false>
+	explicit constexpr
+	tuple(pair<_U1, _U2>&& __in)
+	noexcept(__nothrow_constructible<_U1, _U2>())
+	: _Inherited(std::forward<_U1>(__in.first),
+		     std::forward<_U2>(__in.second)) { }
+
+#if __cplusplus > 202002L
+      template<typename _U1, typename _U2>
+	requires __constructible<_U1&, _U2&>
+	explicit(!__convertible<_U1&, _U2&>)
+	constexpr
+	tuple(pair<_U1, _U2>& __in)
+	noexcept(__nothrow_constructible<_U1&, _U2&>())
+	: _Inherited(__in.first, __in.second) { }
+
+      template<typename _U1, typename _U2>
+	requires __constructible<const _U1, const _U2>
+	explicit(!__convertible<const _U1, const _U2>)
+	constexpr
+	tuple(const pair<_U1, _U2>&& __in)
+	noexcept(__nothrow_constructible<const _U1, const _U2>())
+	: _Inherited(std::forward<const _U1>(__in.first),
+		     std::forward<const _U2>(__in.second)) { }
+#endif // C++23
+
+      // Allocator-extended constructors.
+
+      template<typename _Alloc,
+	       _ImplicitDefaultCtor<is_object<_Alloc>::value, _T1, _T2> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a)
+	: _Inherited(__tag, __a) { }
+
+      template<typename _Alloc, bool _Dummy = true,
+	       _ImplicitCtor<_Dummy, const _T1&, const _T2&> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const _T1& __a1, const _T2& __a2)
+	: _Inherited(__tag, __a, __a1, __a2) { }
+
+      template<typename _Alloc, bool _Dummy = true,
+	       _ExplicitCtor<_Dummy, const _T1&, const _T2&> = false>
+	explicit
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const _T1& __a1, const _T2& __a2)
+	: _Inherited(__tag, __a, __a1, __a2) { }
+
+      template<typename _Alloc, typename _U1, typename _U2,
+	       _ImplicitCtor<true, _U1, _U2> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a, _U1&& __a1, _U2&& __a2)
+	: _Inherited(__tag, __a, std::forward<_U1>(__a1),
+	             std::forward<_U2>(__a2)) { }
+
+      template<typename _Alloc, typename _U1, typename _U2,
+	       _ExplicitCtor<true, _U1, _U2> = false>
+	explicit
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      _U1&& __a1, _U2&& __a2)
+	: _Inherited(__tag, __a, std::forward<_U1>(__a1),
+	             std::forward<_U2>(__a2)) { }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
+	: _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
+
+      template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
+	: _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
+
+      template<typename _Alloc, typename _U1, typename _U2,
+	       _ImplicitCtor<true, const _U1&, const _U2&> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const tuple<_U1, _U2>& __in)
+	: _Inherited(__tag, __a,
+	             static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in))
+	{ }
+
+      template<typename _Alloc, typename _U1, typename _U2,
+	       _ExplicitCtor<true, const _U1&, const _U2&> = false>
+	explicit
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const tuple<_U1, _U2>& __in)
+	: _Inherited(__tag, __a,
+	             static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in))
+	{ }
+
+      template<typename _Alloc, typename _U1, typename _U2,
+	       _ImplicitCtor<true, _U1, _U2> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a, tuple<_U1, _U2>&& __in)
+	: _Inherited(__tag, __a, static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in))
+	{ }
+
+      template<typename _Alloc, typename _U1, typename _U2,
+	       _ExplicitCtor<true, _U1, _U2> = false>
+	explicit
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a, tuple<_U1, _U2>&& __in)
+	: _Inherited(__tag, __a, static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in))
+	{ }
+
+#if __cplusplus > 202002L
+      template<typename _Alloc, typename _U1, typename _U2>
+	requires __constructible<_U1&, _U2&>
+	explicit(!__convertible<_U1&, _U2&>)
+	constexpr
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      tuple<_U1, _U2>& __in)
+	: _Inherited(__tag, __a,
+	             static_cast<_Tuple_impl<0, _U1, _U2>&>(__in))
+	{ }
+
+      template<typename _Alloc, typename _U1, typename _U2>
+	requires __constructible<const _U1, const _U2>
+	explicit(!__convertible<const _U1, const _U2>)
+	constexpr
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const tuple<_U1, _U2>&& __in)
+	: _Inherited(__tag, __a,
+	             static_cast<const _Tuple_impl<0, _U1, _U2>&&>(__in))
+	{ }
+#endif // C++23
+
+      template<typename _Alloc, typename _U1, typename _U2,
+	       _ImplicitCtor<true, const _U1&, const _U2&> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const pair<_U1, _U2>& __in)
+	: _Inherited(__tag, __a, __in.first, __in.second) { }
+
+      template<typename _Alloc, typename _U1, typename _U2,
+	       _ExplicitCtor<true, const _U1&, const _U2&> = false>
+	explicit
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      const pair<_U1, _U2>& __in)
+	: _Inherited(__tag, __a, __in.first, __in.second) { }
+
+      template<typename _Alloc, typename _U1, typename _U2,
+	       _ImplicitCtor<true, _U1, _U2> = true>
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a, pair<_U1, _U2>&& __in)
+	: _Inherited(__tag, __a, std::forward<_U1>(__in.first),
+		     std::forward<_U2>(__in.second)) { }
+
+      template<typename _Alloc, typename _U1, typename _U2,
+	       _ExplicitCtor<true, _U1, _U2> = false>
+	explicit
+	_GLIBCXX20_CONSTEXPR
+	tuple(allocator_arg_t __tag, const _Alloc& __a, pair<_U1, _U2>&& __in)
+	: _Inherited(__tag, __a, std::forward<_U1>(__in.first),
+		     std::forward<_U2>(__in.second)) { }
+
+#if __cplusplus > 202002L
+      template<typename _Alloc, typename _U1, typename _U2>
+	requires __constructible<_U1&, _U2&>
+	explicit(!__convertible<_U1&, _U2&>)
+	constexpr
+	tuple(allocator_arg_t __tag, const _Alloc& __a,
+	      pair<_U1, _U2>& __in)
+	: _Inherited(__tag, __a, __in.first, __in.second) { }
+
+      template<typename _Alloc, typename _U1, typename _U2>
+	requires __constructible<const _U1, const _U2>
+	explicit(!__convertible<const _U1, const _U2>)
+	constexpr
+	tuple(allocator_arg_t __tag, const _Alloc& __a, const pair<_U1, _U2>&& __in)
+	: _Inherited(__tag, __a, std::forward<const _U1>(__in.first),
+		     std::forward<const _U2>(__in.second)) { }
+#endif // C++23
+
+      // Tuple assignment.
+
+      _GLIBCXX20_CONSTEXPR
+      tuple&
+      operator=(__conditional_t<__assignable<const _T1&, const _T2&>(),
+				const tuple&,
+				const __nonesuch&> __in)
+      noexcept(__nothrow_assignable<const _T1&, const _T2&>())
+      {
+	this->_M_assign(__in);
+	return *this;
+      }
+
+      _GLIBCXX20_CONSTEXPR
+      tuple&
+      operator=(__conditional_t<__assignable<_T1, _T2>(),
+				tuple&&,
+				__nonesuch&&> __in)
+      noexcept(__nothrow_assignable<_T1, _T2>())
+      {
+	this->_M_assign(std::move(__in));
+	return *this;
+      }
+
+      template<typename _U1, typename _U2>
+	_GLIBCXX20_CONSTEXPR
+	__enable_if_t<__assignable<const _U1&, const _U2&>(), tuple&>
+	operator=(const tuple<_U1, _U2>& __in)
+	noexcept(__nothrow_assignable<const _U1&, const _U2&>())
+	{
+	  this->_M_assign(__in);
+	  return *this;
+	}
+
+      template<typename _U1, typename _U2>
+	_GLIBCXX20_CONSTEXPR
+	__enable_if_t<__assignable<_U1, _U2>(), tuple&>
+	operator=(tuple<_U1, _U2>&& __in)
+	noexcept(__nothrow_assignable<_U1, _U2>())
+	{
+	  this->_M_assign(std::move(__in));
+	  return *this;
+	}
+
+#if __cplusplus > 202002L
+      constexpr const tuple&
+      operator=(const tuple& __in) const
+      requires is_copy_assignable_v<const _T1> && is_copy_assignable_v<const _T2>
+      {
+	this->_M_assign(__in);
+	return *this;
+      }
+
+      constexpr const tuple&
+      operator=(tuple&& __in) const
+      requires is_assignable_v<const _T1&, _T1> && is_assignable_v<const _T2, _T2>
+      {
+	this->_M_assign(std::move(__in));
+	return *this;
+      }
+
+      template<typename _U1, typename _U2>
+	constexpr const tuple&
+	operator=(const tuple<_U1, _U2>& __in) const
+	requires is_assignable_v<const _T1&, const _U1&>
+	  && is_assignable_v<const _T2&, const _U2&>
+	{
+	  this->_M_assign(__in);
+	  return *this;
+	}
+
+      template<typename _U1, typename _U2>
+	constexpr const tuple&
+	operator=(tuple<_U1, _U2>&& __in) const
+	requires is_assignable_v<const _T1&, _U1>
+	  && is_assignable_v<const _T2&, _U2>
+	{
+	  this->_M_assign(std::move(__in));
+	  return *this;
+	}
+#endif // C++23
+
+      template<typename _U1, typename _U2>
+	_GLIBCXX20_CONSTEXPR
+	__enable_if_t<__assignable<const _U1&, const _U2&>(), tuple&>
+	operator=(const pair<_U1, _U2>& __in)
+	noexcept(__nothrow_assignable<const _U1&, const _U2&>())
+	{
+	  this->_M_head(*this) = __in.first;
+	  this->_M_tail(*this)._M_head(*this) = __in.second;
+	  return *this;
+	}
+
+      template<typename _U1, typename _U2>
+	_GLIBCXX20_CONSTEXPR
+	__enable_if_t<__assignable<_U1, _U2>(), tuple&>
+	operator=(pair<_U1, _U2>&& __in)
+	noexcept(__nothrow_assignable<_U1, _U2>())
+	{
+	  this->_M_head(*this) = std::forward<_U1>(__in.first);
+	  this->_M_tail(*this)._M_head(*this) = std::forward<_U2>(__in.second);
+	  return *this;
+	}
+
+#if __cplusplus > 202002L
+      template<typename _U1, typename _U2>
+	constexpr const tuple&
+	operator=(const pair<_U1, _U2>& __in) const
+	requires is_assignable_v<const _T1&, const _U1&>
+	  && is_assignable_v<const _T2&, const _U2&>
+	{
+	  this->_M_head(*this) = __in.first;
+	  this->_M_tail(*this)._M_head(*this) = __in.second;
+	  return *this;
+	}
+
+      template<typename _U1, typename _U2>
+	constexpr const tuple&
+	operator=(pair<_U1, _U2>&& __in) const
+	requires is_assignable_v<const _T1&, _U1>
+	  && is_assignable_v<const _T2&, _U2>
+	{
+	  this->_M_head(*this) = std::forward<_U1>(__in.first);
+	  this->_M_tail(*this)._M_head(*this) = std::forward<_U2>(__in.second);
+	  return *this;
+	}
+#endif // C++23
+
+      _GLIBCXX20_CONSTEXPR
+      void
+      swap(tuple& __in)
+      noexcept(__and_<__is_nothrow_swappable<_T1>,
+		      __is_nothrow_swappable<_T2>>::value)
+      { _Inherited::_M_swap(__in); }
+
+#if __cplusplus > 202002L
+      constexpr void
+      swap(const tuple& __in) const
+      noexcept(__and_v<__is_nothrow_swappable<const _T1>,
+		       __is_nothrow_swappable<const _T2>>)
+      requires is_swappable_v<const _T1> && is_swappable_v<const _T2>
+      { _Inherited::_M_swap(__in); }
+#endif // C++23
+    };
+
+
+  /// class tuple_size
+  template<typename... _Elements>
+    struct tuple_size<tuple<_Elements...>>
+    : public integral_constant<size_t, sizeof...(_Elements)> { };
+
+#if __cplusplus >= 201703L
+  template<typename... _Types>
+    inline constexpr size_t tuple_size_v<tuple<_Types...>>
+      = sizeof...(_Types);
+
+  template<typename... _Types>
+    inline constexpr size_t tuple_size_v<const tuple<_Types...>>
+      = sizeof...(_Types);
+#endif
+
+  /// Trait to get the Ith element type from a tuple.
+  template<size_t __i, typename... _Types>
+    struct tuple_element<__i, tuple<_Types...>>
+    {
+      static_assert(__i < sizeof...(_Types), "tuple index must be in range");
+
+      using type = typename _Nth_type<__i, _Types...>::type;
+    };
+
+  template<size_t __i, typename _Head, typename... _Tail>
+    constexpr _Head&
+    __get_helper(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
+    { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
+
+  template<size_t __i, typename _Head, typename... _Tail>
+    constexpr const _Head&
+    __get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
+    { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
+
+  // Deleted overload to improve diagnostics for invalid indices
+  template<size_t __i, typename... _Types>
+    __enable_if_t<(__i >= sizeof...(_Types))>
+    __get_helper(const tuple<_Types...>&) = delete;
+
+  /// Return a reference to the ith element of a tuple.
+  template<size_t __i, typename... _Elements>
+    constexpr __tuple_element_t<__i, tuple<_Elements...>>&
+    get(tuple<_Elements...>& __t) noexcept
+    { return std::__get_helper<__i>(__t); }
+
+  /// Return a const reference to the ith element of a const tuple.
+  template<size_t __i, typename... _Elements>
+    constexpr const __tuple_element_t<__i, tuple<_Elements...>>&
+    get(const tuple<_Elements...>& __t) noexcept
+    { return std::__get_helper<__i>(__t); }
+
+  /// Return an rvalue reference to the ith element of a tuple rvalue.
+  template<size_t __i, typename... _Elements>
+    constexpr __tuple_element_t<__i, tuple<_Elements...>>&&
+    get(tuple<_Elements...>&& __t) noexcept
+    {
+      typedef __tuple_element_t<__i, tuple<_Elements...>> __element_type;
+      return std::forward<__element_type>(std::__get_helper<__i>(__t));
+    }
+
+  /// Return a const rvalue reference to the ith element of a const tuple rvalue.
+  template<size_t __i, typename... _Elements>
+    constexpr const __tuple_element_t<__i, tuple<_Elements...>>&&
+    get(const tuple<_Elements...>&& __t) noexcept
+    {
+      typedef __tuple_element_t<__i, tuple<_Elements...>> __element_type;
+      return std::forward<const __element_type>(std::__get_helper<__i>(__t));
+    }
+
+  /// @cond undocumented
+  // Deleted overload chosen for invalid indices.
+  template<size_t __i, typename... _Elements>
+    constexpr __enable_if_t<(__i >= sizeof...(_Elements))>
+    get(const tuple<_Elements...>&) = delete;
+  /// @endcond
+
+#if __cplusplus >= 201402L
+
+#define __cpp_lib_tuples_by_type 201304L
+
+  /// Return a reference to the unique element of type _Tp of a tuple.
+  template <typename _Tp, typename... _Types>
+    constexpr _Tp&
+    get(tuple<_Types...>& __t) noexcept
+    {
+      constexpr size_t __idx = __find_uniq_type_in_pack<_Tp, _Types...>();
+      static_assert(__idx < sizeof...(_Types),
+	  "the type T in std::get<T> must occur exactly once in the tuple");
+      return std::__get_helper<__idx>(__t);
+    }
+
+  /// Return a reference to the unique element of type _Tp of a tuple rvalue.
+  template <typename _Tp, typename... _Types>
+    constexpr _Tp&&
+    get(tuple<_Types...>&& __t) noexcept
+    {
+      constexpr size_t __idx = __find_uniq_type_in_pack<_Tp, _Types...>();
+      static_assert(__idx < sizeof...(_Types),
+	  "the type T in std::get<T> must occur exactly once in the tuple");
+      return std::forward<_Tp>(std::__get_helper<__idx>(__t));
+    }
+
+  /// Return a const reference to the unique element of type _Tp of a tuple.
+  template <typename _Tp, typename... _Types>
+    constexpr const _Tp&
+    get(const tuple<_Types...>& __t) noexcept
+    {
+      constexpr size_t __idx = __find_uniq_type_in_pack<_Tp, _Types...>();
+      static_assert(__idx < sizeof...(_Types),
+	  "the type T in std::get<T> must occur exactly once in the tuple");
+      return std::__get_helper<__idx>(__t);
+    }
+
+  /// Return a const reference to the unique element of type _Tp of
+  /// a const tuple rvalue.
+  template <typename _Tp, typename... _Types>
+    constexpr const _Tp&&
+    get(const tuple<_Types...>&& __t) noexcept
+    {
+      constexpr size_t __idx = __find_uniq_type_in_pack<_Tp, _Types...>();
+      static_assert(__idx < sizeof...(_Types),
+	  "the type T in std::get<T> must occur exactly once in the tuple");
+      return std::forward<const _Tp>(std::__get_helper<__idx>(__t));
+    }
+#endif
+
+  // This class performs the comparison operations on tuples
+  template<typename _Tp, typename _Up, size_t __i, size_t __size>
+    struct __tuple_compare
+    {
+      static constexpr bool
+      __eq(const _Tp& __t, const _Up& __u)
+      {
+	return bool(std::get<__i>(__t) == std::get<__i>(__u))
+	  && __tuple_compare<_Tp, _Up, __i + 1, __size>::__eq(__t, __u);
+      }
+
+      static constexpr bool
+      __less(const _Tp& __t, const _Up& __u)
+      {
+	return bool(std::get<__i>(__t) < std::get<__i>(__u))
+	  || (!bool(std::get<__i>(__u) < std::get<__i>(__t))
+	      && __tuple_compare<_Tp, _Up, __i + 1, __size>::__less(__t, __u));
+      }
+    };
+
+  template<typename _Tp, typename _Up, size_t __size>
+    struct __tuple_compare<_Tp, _Up, __size, __size>
+    {
+      static constexpr bool
+      __eq(const _Tp&, const _Up&) { return true; }
+
+      static constexpr bool
+      __less(const _Tp&, const _Up&) { return false; }
+    };
+
+  template<typename... _TElements, typename... _UElements>
+    constexpr bool
+    operator==(const tuple<_TElements...>& __t,
+	       const tuple<_UElements...>& __u)
+    {
+      static_assert(sizeof...(_TElements) == sizeof...(_UElements),
+	  "tuple objects can only be compared if they have equal sizes.");
+      using __compare = __tuple_compare<tuple<_TElements...>,
+					tuple<_UElements...>,
+					0, sizeof...(_TElements)>;
+      return __compare::__eq(__t, __u);
+    }
+
+#if __cpp_lib_three_way_comparison
+  template<typename _Cat, typename _Tp, typename _Up>
+    constexpr _Cat
+    __tuple_cmp(const _Tp&, const _Up&, index_sequence<>)
+    { return _Cat::equivalent; }
+
+  template<typename _Cat, typename _Tp, typename _Up,
+	   size_t _Idx0, size_t... _Idxs>
+    constexpr _Cat
+    __tuple_cmp(const _Tp& __t, const _Up& __u,
+		index_sequence<_Idx0, _Idxs...>)
+    {
+      auto __c
+	= __detail::__synth3way(std::get<_Idx0>(__t), std::get<_Idx0>(__u));
+      if (__c != 0)
+	return __c;
+      return std::__tuple_cmp<_Cat>(__t, __u, index_sequence<_Idxs...>());
+    }
+
+  template<typename... _Tps, typename... _Ups>
+    constexpr
+    common_comparison_category_t<__detail::__synth3way_t<_Tps, _Ups>...>
+    operator<=>(const tuple<_Tps...>& __t, const tuple<_Ups...>& __u)
+    {
+      using _Cat
+	= common_comparison_category_t<__detail::__synth3way_t<_Tps, _Ups>...>;
+      return std::__tuple_cmp<_Cat>(__t, __u, index_sequence_for<_Tps...>());
+    }
+#else
+  template<typename... _TElements, typename... _UElements>
+    constexpr bool
+    operator<(const tuple<_TElements...>& __t,
+	      const tuple<_UElements...>& __u)
+    {
+      static_assert(sizeof...(_TElements) == sizeof...(_UElements),
+	  "tuple objects can only be compared if they have equal sizes.");
+      using __compare = __tuple_compare<tuple<_TElements...>,
+					tuple<_UElements...>,
+					0, sizeof...(_TElements)>;
+      return __compare::__less(__t, __u);
+    }
+
+  template<typename... _TElements, typename... _UElements>
+    constexpr bool
+    operator!=(const tuple<_TElements...>& __t,
+	       const tuple<_UElements...>& __u)
+    { return !(__t == __u); }
+
+  template<typename... _TElements, typename... _UElements>
+    constexpr bool
+    operator>(const tuple<_TElements...>& __t,
+	      const tuple<_UElements...>& __u)
+    { return __u < __t; }
+
+  template<typename... _TElements, typename... _UElements>
+    constexpr bool
+    operator<=(const tuple<_TElements...>& __t,
+	       const tuple<_UElements...>& __u)
+    { return !(__u < __t); }
+
+  template<typename... _TElements, typename... _UElements>
+    constexpr bool
+    operator>=(const tuple<_TElements...>& __t,
+	       const tuple<_UElements...>& __u)
+    { return !(__t < __u); }
+#endif // three_way_comparison
+
+  // NB: DR 705.
+  /// Create a tuple containing copies of the arguments
+  template<typename... _Elements>
+    constexpr tuple<typename __decay_and_strip<_Elements>::__type...>
+    make_tuple(_Elements&&... __args)
+    {
+      typedef tuple<typename __decay_and_strip<_Elements>::__type...>
+	__result_type;
+      return __result_type(std::forward<_Elements>(__args)...);
+    }
+
+  // _GLIBCXX_RESOLVE_LIB_DEFECTS
+  // 2275. Why is forward_as_tuple not constexpr?
+  /// Create a tuple of lvalue or rvalue references to the arguments
+  template<typename... _Elements>
+    constexpr tuple<_Elements&&...>
+    forward_as_tuple(_Elements&&... __args) noexcept
+    { return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }
+
+  // Declarations of std::array and its std::get overloads, so that
+  // std::tuple_cat can use them if <tuple> is included before <array>.
+
+  template<typename _Tp, size_t _Nm> struct array;
+
+  template<size_t _Int, typename _Tp, size_t _Nm>
+    constexpr _Tp&
+    get(array<_Tp, _Nm>&) noexcept;
+
+  template<size_t _Int, typename _Tp, size_t _Nm>
+    constexpr _Tp&&
+    get(array<_Tp, _Nm>&&) noexcept;
+
+  template<size_t _Int, typename _Tp, size_t _Nm>
+    constexpr const _Tp&
+    get(const array<_Tp, _Nm>&) noexcept;
+
+  template<size_t _Int, typename _Tp, size_t _Nm>
+    constexpr const _Tp&&
+    get(const array<_Tp, _Nm>&&) noexcept;
+
+  /// @cond undocumented
+  template<size_t, typename, typename, size_t>
+    struct __make_tuple_impl;
+
+  template<size_t _Idx, typename _Tuple, typename... _Tp, size_t _Nm>
+    struct __make_tuple_impl<_Idx, tuple<_Tp...>, _Tuple, _Nm>
+    : __make_tuple_impl<_Idx + 1,
+			tuple<_Tp..., __tuple_element_t<_Idx, _Tuple>>,
+			_Tuple, _Nm>
+    { };
+
+  template<size_t _Nm, typename _Tuple, typename... _Tp>
+    struct __make_tuple_impl<_Nm, tuple<_Tp...>, _Tuple, _Nm>
+    {
+      typedef tuple<_Tp...> __type;
+    };
+
+  template<typename _Tuple>
+    struct __do_make_tuple
+    : __make_tuple_impl<0, tuple<>, _Tuple, tuple_size<_Tuple>::value>
+    { };
+
+  // Returns the std::tuple equivalent of a tuple-like type.
+  template<typename _Tuple>
+    struct __make_tuple
+    : public __do_make_tuple<__remove_cvref_t<_Tuple>>
+    { };
+
+  // Combines several std::tuple's into a single one.
+  template<typename...>
+    struct __combine_tuples;
+
+  template<>
+    struct __combine_tuples<>
+    {
+      typedef tuple<> __type;
+    };
+
+  template<typename... _Ts>
+    struct __combine_tuples<tuple<_Ts...>>
+    {
+      typedef tuple<_Ts...> __type;
+    };
+
+  template<typename... _T1s, typename... _T2s, typename... _Rem>
+    struct __combine_tuples<tuple<_T1s...>, tuple<_T2s...>, _Rem...>
+    {
+      typedef typename __combine_tuples<tuple<_T1s..., _T2s...>,
+					_Rem...>::__type __type;
+    };
+
+  // Computes the result type of tuple_cat given a set of tuple-like types.
+  template<typename... _Tpls>
+    struct __tuple_cat_result
+    {
+      typedef typename __combine_tuples
+        <typename __make_tuple<_Tpls>::__type...>::__type __type;
+    };
+
+  // Helper to determine the index set for the first tuple-like
+  // type of a given set.
+  template<typename...>
+    struct __make_1st_indices;
+
+  template<>
+    struct __make_1st_indices<>
+    {
+      typedef _Index_tuple<> __type;
+    };
+
+  template<typename _Tp, typename... _Tpls>
+    struct __make_1st_indices<_Tp, _Tpls...>
+    {
+      typedef typename _Build_index_tuple<tuple_size<
+	typename remove_reference<_Tp>::type>::value>::__type __type;
+    };
+
+  // Performs the actual concatenation by step-wise expanding tuple-like
+  // objects into the elements,  which are finally forwarded into the
+  // result tuple.
+  template<typename _Ret, typename _Indices, typename... _Tpls>
+    struct __tuple_concater;
+
+  template<typename _Ret, size_t... _Is, typename _Tp, typename... _Tpls>
+    struct __tuple_concater<_Ret, _Index_tuple<_Is...>, _Tp, _Tpls...>
+    {
+      template<typename... _Us>
+        static constexpr _Ret
+        _S_do(_Tp&& __tp, _Tpls&&... __tps, _Us&&... __us)
+        {
+	  typedef typename __make_1st_indices<_Tpls...>::__type __idx;
+	  typedef __tuple_concater<_Ret, __idx, _Tpls...>      __next;
+	  return __next::_S_do(std::forward<_Tpls>(__tps)...,
+			       std::forward<_Us>(__us)...,
+			       std::get<_Is>(std::forward<_Tp>(__tp))...);
+	}
+    };
+
+  template<typename _Ret>
+    struct __tuple_concater<_Ret, _Index_tuple<>>
+    {
+      template<typename... _Us>
+	static constexpr _Ret
+	_S_do(_Us&&... __us)
+        {
+	  return _Ret(std::forward<_Us>(__us)...);
+	}
+    };
+
+  template<typename... _Tps>
+    struct __is_tuple_like_impl<tuple<_Tps...>> : true_type
+    { };
+  /// @endcond
+
+  /// Create a `tuple` containing all elements from multiple tuple-like objects
+  template<typename... _Tpls, typename = typename
+           enable_if<__and_<__is_tuple_like<_Tpls>...>::value>::type>
+    constexpr auto
+    tuple_cat(_Tpls&&... __tpls)
+    -> typename __tuple_cat_result<_Tpls...>::__type
+    {
+      typedef typename __tuple_cat_result<_Tpls...>::__type __ret;
+      typedef typename __make_1st_indices<_Tpls...>::__type __idx;
+      typedef __tuple_concater<__ret, __idx, _Tpls...> __concater;
+      return __concater::_S_do(std::forward<_Tpls>(__tpls)...);
+    }
+
+  // _GLIBCXX_RESOLVE_LIB_DEFECTS
+  // 2301. Why is tie not constexpr?
+  /// Return a tuple of lvalue references bound to the arguments
+  template<typename... _Elements>
+    constexpr tuple<_Elements&...>
+    tie(_Elements&... __args) noexcept
+    { return tuple<_Elements&...>(__args...); }
+
+  /// Exchange the values of two tuples
+  template<typename... _Elements>
+    _GLIBCXX20_CONSTEXPR
+    inline
+#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
+    // Constrained free swap overload, see p0185r1
+    typename enable_if<__and_<__is_swappable<_Elements>...>::value
+      >::type
+#else
+    void
+#endif
+    swap(tuple<_Elements...>& __x, tuple<_Elements...>& __y)
+    noexcept(noexcept(__x.swap(__y)))
+    { __x.swap(__y); }
+
+#if __cplusplus > 202002L
+  template<typename... _Elements>
+    requires (is_swappable_v<const _Elements> && ...)
+    constexpr void
+    swap(const tuple<_Elements...>& __x, const tuple<_Elements...>& __y)
+    noexcept(noexcept(__x.swap(__y)))
+    { __x.swap(__y); }
+#endif // C++23
+
+#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
+  /// Exchange the values of two const tuples (if const elements can be swapped)
+  template<typename... _Elements>
+    _GLIBCXX20_CONSTEXPR
+    typename enable_if<!__and_<__is_swappable<_Elements>...>::value>::type
+    swap(tuple<_Elements...>&, tuple<_Elements...>&) = delete;
+#endif
+
+  // A class (and instance) which can be used in 'tie' when an element
+  // of a tuple is not required.
+  // _GLIBCXX14_CONSTEXPR
+  // 2933. PR for LWG 2773 could be clearer
+  struct _Swallow_assign
+  {
+    template<class _Tp>
+      _GLIBCXX14_CONSTEXPR const _Swallow_assign&
+      operator=(const _Tp&) const
+      { return *this; }
+  };
+
+  // _GLIBCXX_RESOLVE_LIB_DEFECTS
+  // 2773. Making std::ignore constexpr
+  /** Used with `std::tie` to ignore an element of a tuple
+   *
+   * When using `std::tie` to assign the elements of a tuple to variables,
+   * unwanted elements can be ignored by using `std::ignore`. For example:
+   *
+   * ```
+   * int x, y;
+   * std::tie(x, std::ignore, y) = std::make_tuple(1, 2, 3);
+   * ```
+   *
+   * This assignment will perform `x=1; std::ignore=2; y=3;` which results
+   * in the second element being ignored.
+   *
+   * @since C++11
+   */
+  _GLIBCXX17_INLINE constexpr _Swallow_assign ignore{};
+
+  /// Partial specialization for tuples
+  template<typename... _Types, typename _Alloc>
+    struct uses_allocator<tuple<_Types...>, _Alloc> : true_type { };
+
+  // See stl_pair.h...
+  /** "piecewise construction" using a tuple of arguments for each member.
+   *
+   * @param __first Arguments for the first member of the pair.
+   * @param __second Arguments for the second member of the pair.
+   *
+   * The elements of each tuple will be used as the constructor arguments
+   * for the data members of the pair.
+  */
+  template<class _T1, class _T2>
+    template<typename... _Args1, typename... _Args2>
+      _GLIBCXX20_CONSTEXPR
+      inline
+      pair<_T1, _T2>::
+      pair(piecewise_construct_t,
+	   tuple<_Args1...> __first, tuple<_Args2...> __second)
+      : pair(__first, __second,
+	     typename _Build_index_tuple<sizeof...(_Args1)>::__type(),
+	     typename _Build_index_tuple<sizeof...(_Args2)>::__type())
+      { }
+
+  template<class _T1, class _T2>
+    template<typename... _Args1, size_t... _Indexes1,
+	     typename... _Args2, size_t... _Indexes2>
+      _GLIBCXX20_CONSTEXPR inline
+      pair<_T1, _T2>::
+      pair(tuple<_Args1...>& __tuple1, tuple<_Args2...>& __tuple2,
+	   _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>)
+      : first(std::forward<_Args1>(std::get<_Indexes1>(__tuple1))...),
+	second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)
+      { }
+
+#if __cplusplus >= 201703L
+
+  // Unpack a std::tuple into a type trait and use its value.
+  // For cv std::tuple<_Up> the result is _Trait<_Tp, cv _Up...>::value.
+  // For cv std::tuple<_Up>& the result is _Trait<_Tp, cv _Up&...>::value.
+  // Otherwise the result is false (because we don't know if std::get throws).
+  template<template<typename...> class _Trait, typename _Tp, typename _Tuple>
+    inline constexpr bool __unpack_std_tuple = false;
+
+  template<template<typename...> class _Trait, typename _Tp, typename... _Up>
+    inline constexpr bool __unpack_std_tuple<_Trait, _Tp, tuple<_Up...>>
+      = _Trait<_Tp, _Up...>::value;
+
+  template<template<typename...> class _Trait, typename _Tp, typename... _Up>
+    inline constexpr bool __unpack_std_tuple<_Trait, _Tp, tuple<_Up...>&>
+      = _Trait<_Tp, _Up&...>::value;
+
+  template<template<typename...> class _Trait, typename _Tp, typename... _Up>
+    inline constexpr bool __unpack_std_tuple<_Trait, _Tp, const tuple<_Up...>>
+      = _Trait<_Tp, const _Up...>::value;
+
+  template<template<typename...> class _Trait, typename _Tp, typename... _Up>
+    inline constexpr bool __unpack_std_tuple<_Trait, _Tp, const tuple<_Up...>&>
+      = _Trait<_Tp, const _Up&...>::value;
+
+# define __cpp_lib_apply 201603L
+
+  template <typename _Fn, typename _Tuple, size_t... _Idx>
+    constexpr decltype(auto)
+    __apply_impl(_Fn&& __f, _Tuple&& __t, index_sequence<_Idx...>)
+    {
+      return std::__invoke(std::forward<_Fn>(__f),
+			   std::get<_Idx>(std::forward<_Tuple>(__t))...);
+    }
+
+  template <typename _Fn, typename _Tuple>
+    constexpr decltype(auto)
+    apply(_Fn&& __f, _Tuple&& __t)
+    noexcept(__unpack_std_tuple<is_nothrow_invocable, _Fn, _Tuple>)
+    {
+      using _Indices
+	= make_index_sequence<tuple_size_v<remove_reference_t<_Tuple>>>;
+      return std::__apply_impl(std::forward<_Fn>(__f),
+			       std::forward<_Tuple>(__t),
+			       _Indices{});
+    }
+
+#define __cpp_lib_make_from_tuple  201606L
+
+  template <typename _Tp, typename _Tuple, size_t... _Idx>
+    constexpr _Tp
+    __make_from_tuple_impl(_Tuple&& __t, index_sequence<_Idx...>)
+    { return _Tp(std::get<_Idx>(std::forward<_Tuple>(__t))...); }
+
+  template <typename _Tp, typename _Tuple>
+    constexpr _Tp
+    make_from_tuple(_Tuple&& __t)
+    noexcept(__unpack_std_tuple<is_nothrow_constructible, _Tp, _Tuple>)
+    {
+      constexpr size_t __n = tuple_size_v<remove_reference_t<_Tuple>>;
+#if __has_builtin(__reference_constructs_from_temporary)
+      if constexpr (__n == 1)
+	{
+	  using _Elt = decltype(std::get<0>(std::declval<_Tuple>()));
+	  static_assert(!__reference_constructs_from_temporary(_Tp, _Elt));
+	}
+#endif
+      return __make_from_tuple_impl<_Tp>(std::forward<_Tuple>(__t),
+					 make_index_sequence<__n>{});
+    }
+#endif // C++17
+
+#if __cplusplus > 202002L
+  template<typename... _TTypes, typename... _UTypes,
+	   template<typename> class _TQual, template<typename> class _UQual>
+    requires requires { typename tuple<common_reference_t<_TQual<_TTypes>, _UQual<_UTypes>>...>; }
+  struct basic_common_reference<tuple<_TTypes...>, tuple<_UTypes...>, _TQual, _UQual>
+  { using type = tuple<common_reference_t<_TQual<_TTypes>, _UQual<_UTypes>>...>; };
+
+  template<typename... _TTypes, typename... _UTypes>
+    requires requires { typename tuple<common_type_t<_TTypes, _UTypes>...>; }
+  struct common_type<tuple<_TTypes...>, tuple<_UTypes...>>
+  { using type = tuple<common_type_t<_TTypes, _UTypes>...>; };
+#endif // C++23
+
+  /// @}
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+
+#endif // C++11
+
+#endif // _GLIBCXX_TUPLE