Restoring authorship annotation for Andrey Khalyavin <halyavin@gmail.com>. Commit 1 of 2.

1 files changed, 1560 insertions, 1560 deletions

diff --git a/contrib/libs/cxxsupp/libcxx/include/tuple b/contrib/libs/cxxsupp/libcxx/include/tuple
index 9b127953b3..1e2cd6c039 100644
--- a/contrib/libs/cxxsupp/libcxx/include/tuple
+++ b/contrib/libs/cxxsupp/libcxx/include/tuple
@@ -1,387 +1,387 @@
-// -*- C++ -*-
-//===--------------------------- tuple ------------------------------------===//
-//
+// -*- C++ -*- 
+//===--------------------------- tuple ------------------------------------===// 
+// 
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef _LIBCPP_TUPLE
-#define _LIBCPP_TUPLE
-
-/*
-    tuple synopsis
-
-namespace std
-{
-
-template <class... T>
-class tuple {
-public:
-    explicit(see-below) constexpr tuple();
-    explicit(see-below) tuple(const T&...);  // constexpr in C++14
-    template <class... U>
-        explicit(see-below) tuple(U&&...);  // constexpr in C++14
-    tuple(const tuple&) = default;
-    tuple(tuple&&) = default;
-    template <class... U>
-        explicit(see-below) tuple(const tuple<U...>&);  // constexpr in C++14
-    template <class... U>
-        explicit(see-below) tuple(tuple<U...>&&);  // constexpr in C++14
-    template <class U1, class U2>
-        explicit(see-below) tuple(const pair<U1, U2>&); // iff sizeof...(T) == 2 // constexpr in C++14
-    template <class U1, class U2>
-        explicit(see-below) tuple(pair<U1, U2>&&); // iff sizeof...(T) == 2  // constexpr in C++14
-
-    // allocator-extended constructors
-    template <class Alloc>
-        tuple(allocator_arg_t, const Alloc& a);
-    template <class Alloc>
-        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, const T&...);          // constexpr in C++20
-    template <class Alloc, class... U>
-        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, U&&...);               // constexpr in C++20
-    template <class Alloc>
-        tuple(allocator_arg_t, const Alloc& a, const tuple&);                             // constexpr in C++20
-    template <class Alloc>
-        tuple(allocator_arg_t, const Alloc& a, tuple&&);                                  // constexpr in C++20
-    template <class Alloc, class... U>
-        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, const tuple<U...>&);   // constexpr in C++20
-    template <class Alloc, class... U>
-        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, tuple<U...>&&);        // constexpr in C++20
-    template <class Alloc, class U1, class U2>
-        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, const pair<U1, U2>&);  // constexpr in C++20
-    template <class Alloc, class U1, class U2>
-        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, pair<U1, U2>&&);       // constexpr in C++20
-
-    tuple& operator=(const tuple&);                                                       // constexpr in C++20
-    tuple& operator=(tuple&&) noexcept(is_nothrow_move_assignable_v<T> && ...);           // constexpr in C++20
-    template <class... U>
-        tuple& operator=(const tuple<U...>&);                                             // constexpr in C++20
-    template <class... U>
-        tuple& operator=(tuple<U...>&&);                                                  // constexpr in C++20
-    template <class U1, class U2>
-        tuple& operator=(const pair<U1, U2>&); // iff sizeof...(T) == 2                   // constexpr in C++20
-    template <class U1, class U2>
-        tuple& operator=(pair<U1, U2>&&); // iff sizeof...(T) == 2                        // constexpr in C++20
-
-    template<class U, size_t N>
-        tuple& operator=(array<U, N> const&) // iff sizeof...(T) == N, EXTENSION
-    template<class U, size_t N>
-        tuple& operator=(array<U, N>&&) // iff sizeof...(T) == N, EXTENSION
-
-    void swap(tuple&) noexcept(AND(swap(declval<T&>(), declval<T&>())...));               // constexpr in C++20
-};
-
-template <class ...T>
-tuple(T...) -> tuple<T...>;                                         // since C++17
-template <class T1, class T2>
-tuple(pair<T1, T2>) -> tuple<T1, T2>;                               // since C++17
-template <class Alloc, class ...T>
-tuple(allocator_arg_t, Alloc, T...) -> tuple<T...>;                 // since C++17
-template <class Alloc, class T1, class T2>
-tuple(allocator_arg_t, Alloc, pair<T1, T2>) -> tuple<T1, T2>;       // since C++17
-template <class Alloc, class ...T>
-tuple(allocator_arg_t, Alloc, tuple<T...>) -> tuple<T...>;          // since C++17
-
-inline constexpr unspecified ignore;
-
-template <class... T> tuple<V...>  make_tuple(T&&...); // constexpr in C++14
-template <class... T> tuple<ATypes...> forward_as_tuple(T&&...) noexcept; // constexpr in C++14
-template <class... T> tuple<T&...> tie(T&...) noexcept; // constexpr in C++14
-template <class... Tuples> tuple<CTypes...> tuple_cat(Tuples&&... tpls); // constexpr in C++14
-
-// [tuple.apply], calling a function with a tuple of arguments:
-template <class F, class Tuple>
-  constexpr decltype(auto) apply(F&& f, Tuple&& t); // C++17
-template <class T, class Tuple>
-  constexpr T make_from_tuple(Tuple&& t); // C++17
-
-// 20.4.1.4, tuple helper classes:
+// 
+//===----------------------------------------------------------------------===// 
+ 
+#ifndef _LIBCPP_TUPLE 
+#define _LIBCPP_TUPLE 
+ 
+/* 
+    tuple synopsis 
+ 
+namespace std 
+{ 
+ 
+template <class... T> 
+class tuple { 
+public: 
+    explicit(see-below) constexpr tuple(); 
+    explicit(see-below) tuple(const T&...);  // constexpr in C++14 
+    template <class... U> 
+        explicit(see-below) tuple(U&&...);  // constexpr in C++14 
+    tuple(const tuple&) = default; 
+    tuple(tuple&&) = default; 
+    template <class... U> 
+        explicit(see-below) tuple(const tuple<U...>&);  // constexpr in C++14 
+    template <class... U> 
+        explicit(see-below) tuple(tuple<U...>&&);  // constexpr in C++14 
+    template <class U1, class U2> 
+        explicit(see-below) tuple(const pair<U1, U2>&); // iff sizeof...(T) == 2 // constexpr in C++14 
+    template <class U1, class U2> 
+        explicit(see-below) tuple(pair<U1, U2>&&); // iff sizeof...(T) == 2  // constexpr in C++14 
+ 
+    // allocator-extended constructors 
+    template <class Alloc> 
+        tuple(allocator_arg_t, const Alloc& a); 
+    template <class Alloc> 
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, const T&...);          // constexpr in C++20 
+    template <class Alloc, class... U> 
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, U&&...);               // constexpr in C++20 
+    template <class Alloc> 
+        tuple(allocator_arg_t, const Alloc& a, const tuple&);                             // constexpr in C++20 
+    template <class Alloc> 
+        tuple(allocator_arg_t, const Alloc& a, tuple&&);                                  // constexpr in C++20 
+    template <class Alloc, class... U> 
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, const tuple<U...>&);   // constexpr in C++20 
+    template <class Alloc, class... U> 
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, tuple<U...>&&);        // constexpr in C++20 
+    template <class Alloc, class U1, class U2> 
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, const pair<U1, U2>&);  // constexpr in C++20 
+    template <class Alloc, class U1, class U2> 
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, pair<U1, U2>&&);       // constexpr in C++20 
+ 
+    tuple& operator=(const tuple&);                                                       // constexpr in C++20 
+    tuple& operator=(tuple&&) noexcept(is_nothrow_move_assignable_v<T> && ...);           // constexpr in C++20 
+    template <class... U> 
+        tuple& operator=(const tuple<U...>&);                                             // constexpr in C++20 
+    template <class... U> 
+        tuple& operator=(tuple<U...>&&);                                                  // constexpr in C++20 
+    template <class U1, class U2> 
+        tuple& operator=(const pair<U1, U2>&); // iff sizeof...(T) == 2                   // constexpr in C++20 
+    template <class U1, class U2> 
+        tuple& operator=(pair<U1, U2>&&); // iff sizeof...(T) == 2                        // constexpr in C++20 
+ 
+    template<class U, size_t N> 
+        tuple& operator=(array<U, N> const&) // iff sizeof...(T) == N, EXTENSION 
+    template<class U, size_t N> 
+        tuple& operator=(array<U, N>&&) // iff sizeof...(T) == N, EXTENSION 
+ 
+    void swap(tuple&) noexcept(AND(swap(declval<T&>(), declval<T&>())...));               // constexpr in C++20 
+}; 
+ 
+template <class ...T> 
+tuple(T...) -> tuple<T...>;                                         // since C++17 
+template <class T1, class T2> 
+tuple(pair<T1, T2>) -> tuple<T1, T2>;                               // since C++17 
+template <class Alloc, class ...T> 
+tuple(allocator_arg_t, Alloc, T...) -> tuple<T...>;                 // since C++17 
+template <class Alloc, class T1, class T2> 
+tuple(allocator_arg_t, Alloc, pair<T1, T2>) -> tuple<T1, T2>;       // since C++17 
+template <class Alloc, class ...T> 
+tuple(allocator_arg_t, Alloc, tuple<T...>) -> tuple<T...>;          // since C++17 
+ 
+inline constexpr unspecified ignore; 
+ 
+template <class... T> tuple<V...>  make_tuple(T&&...); // constexpr in C++14 
+template <class... T> tuple<ATypes...> forward_as_tuple(T&&...) noexcept; // constexpr in C++14 
+template <class... T> tuple<T&...> tie(T&...) noexcept; // constexpr in C++14 
+template <class... Tuples> tuple<CTypes...> tuple_cat(Tuples&&... tpls); // constexpr in C++14 
+ 
+// [tuple.apply], calling a function with a tuple of arguments: 
+template <class F, class Tuple> 
+  constexpr decltype(auto) apply(F&& f, Tuple&& t); // C++17 
+template <class T, class Tuple> 
+  constexpr T make_from_tuple(Tuple&& t); // C++17 
+ 
+// 20.4.1.4, tuple helper classes: 
 template <class T> struct tuple_size; // undefined
 template <class... T> struct tuple_size<tuple<T...>>;
-template <class T>
- inline constexpr size_t tuple_size_v = tuple_size<T>::value; // C++17
-template <size_t I, class T> struct tuple_element; // undefined
-template <size_t I, class... T> struct tuple_element<I, tuple<T...>>;
-template <size_t I, class T>
-  using tuple_element_t = typename tuple_element <I, T>::type; // C++14
-
-// 20.4.1.5, element access:
-template <size_t I, class... T>
-    typename tuple_element<I, tuple<T...>>::type&
-    get(tuple<T...>&) noexcept; // constexpr in C++14
-template <size_t I, class... T>
-    const typename tuple_element<I, tuple<T...>>::type&
-    get(const tuple<T...>&) noexcept; // constexpr in C++14
-template <size_t I, class... T>
-    typename tuple_element<I, tuple<T...>>::type&&
-    get(tuple<T...>&&) noexcept; // constexpr in C++14
-template <size_t I, class... T>
-    const typename tuple_element<I, tuple<T...>>::type&&
-    get(const tuple<T...>&&) noexcept; // constexpr in C++14
-
-template <class T1, class... T>
-    constexpr T1& get(tuple<T...>&) noexcept;  // C++14
-template <class T1, class... T>
-    constexpr const T1& get(const tuple<T...>&) noexcept;   // C++14
-template <class T1, class... T>
-    constexpr T1&& get(tuple<T...>&&) noexcept;   // C++14
-template <class T1, class... T>
-    constexpr const T1&& get(const tuple<T...>&&) noexcept;   // C++14
-
-// 20.4.1.6, relational operators:
-template<class... T, class... U> bool operator==(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
-template<class... T, class... U> bool operator<(const tuple<T...>&, const tuple<U...>&);  // constexpr in C++14
-template<class... T, class... U> bool operator!=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
-template<class... T, class... U> bool operator>(const tuple<T...>&, const tuple<U...>&);  // constexpr in C++14
-template<class... T, class... U> bool operator<=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
-template<class... T, class... U> bool operator>=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
-
-template <class... Types, class Alloc>
-  struct uses_allocator<tuple<Types...>, Alloc>;
-
-template <class... Types>
-  void
-  swap(tuple<Types...>& x, tuple<Types...>& y) noexcept(noexcept(x.swap(y)));
-
-}  // std
-
-*/
-
-#include <__config>
-#include <__functional/unwrap_ref.h>
-#include <__functional_base>
-#include <__memory/allocator_arg_t.h>
-#include <__memory/uses_allocator.h>
-#include <__tuple>
-#include <__utility/forward.h>
-#include <__utility/move.h>
-#include <compare>
-#include <cstddef>
-#include <type_traits>
-#include <utility>
+template <class T> 
+ inline constexpr size_t tuple_size_v = tuple_size<T>::value; // C++17 
+template <size_t I, class T> struct tuple_element; // undefined 
+template <size_t I, class... T> struct tuple_element<I, tuple<T...>>; 
+template <size_t I, class T> 
+  using tuple_element_t = typename tuple_element <I, T>::type; // C++14 
+ 
+// 20.4.1.5, element access: 
+template <size_t I, class... T> 
+    typename tuple_element<I, tuple<T...>>::type& 
+    get(tuple<T...>&) noexcept; // constexpr in C++14 
+template <size_t I, class... T> 
+    const typename tuple_element<I, tuple<T...>>::type& 
+    get(const tuple<T...>&) noexcept; // constexpr in C++14 
+template <size_t I, class... T> 
+    typename tuple_element<I, tuple<T...>>::type&& 
+    get(tuple<T...>&&) noexcept; // constexpr in C++14 
+template <size_t I, class... T> 
+    const typename tuple_element<I, tuple<T...>>::type&& 
+    get(const tuple<T...>&&) noexcept; // constexpr in C++14 
+ 
+template <class T1, class... T> 
+    constexpr T1& get(tuple<T...>&) noexcept;  // C++14 
+template <class T1, class... T> 
+    constexpr const T1& get(const tuple<T...>&) noexcept;   // C++14 
+template <class T1, class... T> 
+    constexpr T1&& get(tuple<T...>&&) noexcept;   // C++14 
+template <class T1, class... T> 
+    constexpr const T1&& get(const tuple<T...>&&) noexcept;   // C++14 
+ 
+// 20.4.1.6, relational operators: 
+template<class... T, class... U> bool operator==(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14 
+template<class... T, class... U> bool operator<(const tuple<T...>&, const tuple<U...>&);  // constexpr in C++14 
+template<class... T, class... U> bool operator!=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14 
+template<class... T, class... U> bool operator>(const tuple<T...>&, const tuple<U...>&);  // constexpr in C++14 
+template<class... T, class... U> bool operator<=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14 
+template<class... T, class... U> bool operator>=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14 
+ 
+template <class... Types, class Alloc> 
+  struct uses_allocator<tuple<Types...>, Alloc>; 
+ 
+template <class... Types> 
+  void 
+  swap(tuple<Types...>& x, tuple<Types...>& y) noexcept(noexcept(x.swap(y))); 
+ 
+}  // std 
+ 
+*/ 
+ 
+#include <__config> 
+#include <__functional/unwrap_ref.h> 
+#include <__functional_base> 
+#include <__memory/allocator_arg_t.h> 
+#include <__memory/uses_allocator.h> 
+#include <__tuple> 
+#include <__utility/forward.h> 
+#include <__utility/move.h> 
+#include <compare> 
+#include <cstddef> 
+#include <type_traits> 
+#include <utility> 
 #include <version>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
-#endif
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-#ifndef _LIBCPP_CXX03_LANG
-
-
-// __tuple_leaf
-
-template <size_t _Ip, class _Hp,
-          bool=is_empty<_Hp>::value && !__libcpp_is_final<_Hp>::value
-         >
-class __tuple_leaf;
-
-template <size_t _Ip, class _Hp, bool _Ep>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-void swap(__tuple_leaf<_Ip, _Hp, _Ep>& __x, __tuple_leaf<_Ip, _Hp, _Ep>& __y)
-    _NOEXCEPT_(__is_nothrow_swappable<_Hp>::value)
-{
-    swap(__x.get(), __y.get());
-}
-
-template <size_t _Ip, class _Hp, bool>
-class __tuple_leaf
-{
-    _Hp __value_;
-
-    template <class _Tp>
-    static constexpr bool __can_bind_reference() {
+ 
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 
+#pragma GCC system_header 
+#endif 
+ 
+_LIBCPP_BEGIN_NAMESPACE_STD 
+ 
+#ifndef _LIBCPP_CXX03_LANG 
+ 
+ 
+// __tuple_leaf 
+ 
+template <size_t _Ip, class _Hp, 
+          bool=is_empty<_Hp>::value && !__libcpp_is_final<_Hp>::value 
+         > 
+class __tuple_leaf; 
+ 
+template <size_t _Ip, class _Hp, bool _Ep> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+void swap(__tuple_leaf<_Ip, _Hp, _Ep>& __x, __tuple_leaf<_Ip, _Hp, _Ep>& __y) 
+    _NOEXCEPT_(__is_nothrow_swappable<_Hp>::value) 
+{ 
+    swap(__x.get(), __y.get()); 
+} 
+ 
+template <size_t _Ip, class _Hp, bool> 
+class __tuple_leaf 
+{ 
+    _Hp __value_; 
+ 
+    template <class _Tp> 
+    static constexpr bool __can_bind_reference() { 
 #if __has_keyword(__reference_binds_to_temporary) && !defined(__CUDACC__)
-      return !__reference_binds_to_temporary(_Hp, _Tp);
-#else
-      return true;
-#endif
-    }
-
-    _LIBCPP_CONSTEXPR_AFTER_CXX11
-    __tuple_leaf& operator=(const __tuple_leaf&);
-public:
-    _LIBCPP_INLINE_VISIBILITY constexpr __tuple_leaf()
-             _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) : __value_()
-       {static_assert(!is_reference<_Hp>::value,
-              "Attempted to default construct a reference element in a tuple");}
-
-    template <class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY constexpr
-        __tuple_leaf(integral_constant<int, 0>, const _Alloc&)
-            : __value_()
-        {static_assert(!is_reference<_Hp>::value,
-              "Attempted to default construct a reference element in a tuple");}
-
-    template <class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY constexpr
-        __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a)
-            : __value_(allocator_arg_t(), __a)
-        {static_assert(!is_reference<_Hp>::value,
-              "Attempted to default construct a reference element in a tuple");}
-
-    template <class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY constexpr
-        __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a)
-            : __value_(__a)
-        {static_assert(!is_reference<_Hp>::value,
-              "Attempted to default construct a reference element in a tuple");}
-
-    template <class _Tp,
-              class = __enable_if_t<
-                  _And<
-                      _IsNotSame<__uncvref_t<_Tp>, __tuple_leaf>,
-                      is_constructible<_Hp, _Tp>
-                    >::value
-                >
-            >
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value))
-            : __value_(_VSTD::forward<_Tp>(__t))
-        {static_assert(__can_bind_reference<_Tp&&>(),
-       "Attempted construction of reference element binds to a temporary whose lifetime has ended");}
-
-    template <class _Tp, class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t)
-            : __value_(_VSTD::forward<_Tp>(__t))
-        {static_assert(__can_bind_reference<_Tp&&>(),
-       "Attempted construction of reference element binds to a temporary whose lifetime has ended");}
-
-    template <class _Tp, class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t)
-            : __value_(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t))
-        {static_assert(!is_reference<_Hp>::value,
-            "Attempted to uses-allocator construct a reference element in a tuple");}
-
-    template <class _Tp, class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t)
-            : __value_(_VSTD::forward<_Tp>(__t), __a)
-        {static_assert(!is_reference<_Hp>::value,
-           "Attempted to uses-allocator construct a reference element in a tuple");}
-
-    __tuple_leaf(const __tuple_leaf& __t) = default;
-    __tuple_leaf(__tuple_leaf&& __t) = default;
-
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    int swap(__tuple_leaf& __t) _NOEXCEPT_(__is_nothrow_swappable<__tuple_leaf>::value)
-    {
-        _VSTD::swap(*this, __t);
-        return 0;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11       _Hp& get()       _NOEXCEPT {return __value_;}
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return __value_;}
-};
-
-template <size_t _Ip, class _Hp>
-class __tuple_leaf<_Ip, _Hp, true>
-    : private _Hp
-{
-    _LIBCPP_CONSTEXPR_AFTER_CXX11
-    __tuple_leaf& operator=(const __tuple_leaf&);
-public:
-    _LIBCPP_INLINE_VISIBILITY constexpr __tuple_leaf()
-             _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) {}
-
-    template <class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY constexpr
-        __tuple_leaf(integral_constant<int, 0>, const _Alloc&) {}
-
-    template <class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY constexpr
-        __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a)
-            : _Hp(allocator_arg_t(), __a) {}
-
-    template <class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY constexpr
-        __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a)
-            : _Hp(__a) {}
-
-    template <class _Tp,
-              class = __enable_if_t<
-                  _And<
-                    _IsNotSame<__uncvref_t<_Tp>, __tuple_leaf>,
-                    is_constructible<_Hp, _Tp>
+      return !__reference_binds_to_temporary(_Hp, _Tp); 
+#else 
+      return true; 
+#endif 
+    } 
+ 
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    __tuple_leaf& operator=(const __tuple_leaf&); 
+public: 
+    _LIBCPP_INLINE_VISIBILITY constexpr __tuple_leaf() 
+             _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) : __value_() 
+       {static_assert(!is_reference<_Hp>::value, 
+              "Attempted to default construct a reference element in a tuple");} 
+ 
+    template <class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY constexpr 
+        __tuple_leaf(integral_constant<int, 0>, const _Alloc&) 
+            : __value_() 
+        {static_assert(!is_reference<_Hp>::value, 
+              "Attempted to default construct a reference element in a tuple");} 
+ 
+    template <class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY constexpr 
+        __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a) 
+            : __value_(allocator_arg_t(), __a) 
+        {static_assert(!is_reference<_Hp>::value, 
+              "Attempted to default construct a reference element in a tuple");} 
+ 
+    template <class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY constexpr 
+        __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a) 
+            : __value_(__a) 
+        {static_assert(!is_reference<_Hp>::value, 
+              "Attempted to default construct a reference element in a tuple");} 
+ 
+    template <class _Tp, 
+              class = __enable_if_t< 
+                  _And< 
+                      _IsNotSame<__uncvref_t<_Tp>, __tuple_leaf>, 
+                      is_constructible<_Hp, _Tp> 
+                    >::value 
+                > 
+            > 
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value)) 
+            : __value_(_VSTD::forward<_Tp>(__t)) 
+        {static_assert(__can_bind_reference<_Tp&&>(), 
+       "Attempted construction of reference element binds to a temporary whose lifetime has ended");} 
+ 
+    template <class _Tp, class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t) 
+            : __value_(_VSTD::forward<_Tp>(__t)) 
+        {static_assert(__can_bind_reference<_Tp&&>(), 
+       "Attempted construction of reference element binds to a temporary whose lifetime has ended");} 
+ 
+    template <class _Tp, class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t) 
+            : __value_(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t)) 
+        {static_assert(!is_reference<_Hp>::value, 
+            "Attempted to uses-allocator construct a reference element in a tuple");} 
+ 
+    template <class _Tp, class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t) 
+            : __value_(_VSTD::forward<_Tp>(__t), __a) 
+        {static_assert(!is_reference<_Hp>::value, 
+           "Attempted to uses-allocator construct a reference element in a tuple");} 
+ 
+    __tuple_leaf(const __tuple_leaf& __t) = default; 
+    __tuple_leaf(__tuple_leaf&& __t) = default; 
+ 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    int swap(__tuple_leaf& __t) _NOEXCEPT_(__is_nothrow_swappable<__tuple_leaf>::value) 
+    { 
+        _VSTD::swap(*this, __t); 
+        return 0; 
+    } 
+ 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11       _Hp& get()       _NOEXCEPT {return __value_;} 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return __value_;} 
+}; 
+ 
+template <size_t _Ip, class _Hp> 
+class __tuple_leaf<_Ip, _Hp, true> 
+    : private _Hp 
+{ 
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    __tuple_leaf& operator=(const __tuple_leaf&); 
+public: 
+    _LIBCPP_INLINE_VISIBILITY constexpr __tuple_leaf() 
+             _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) {} 
+ 
+    template <class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY constexpr 
+        __tuple_leaf(integral_constant<int, 0>, const _Alloc&) {} 
+ 
+    template <class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY constexpr 
+        __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a) 
+            : _Hp(allocator_arg_t(), __a) {} 
+ 
+    template <class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY constexpr 
+        __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a) 
+            : _Hp(__a) {} 
+ 
+    template <class _Tp, 
+              class = __enable_if_t< 
+                  _And< 
+                    _IsNotSame<__uncvref_t<_Tp>, __tuple_leaf>, 
+                    is_constructible<_Hp, _Tp> 
                   >::value
-                >
-            >
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value))
-            : _Hp(_VSTD::forward<_Tp>(__t)) {}
-
-    template <class _Tp, class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY constexpr
-        explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t)
-            : _Hp(_VSTD::forward<_Tp>(__t)) {}
-
-    template <class _Tp, class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY constexpr
-        explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t)
-            : _Hp(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t)) {}
-
-    template <class _Tp, class _Alloc>
-        _LIBCPP_INLINE_VISIBILITY constexpr
-        explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t)
-            : _Hp(_VSTD::forward<_Tp>(__t), __a) {}
-
-    __tuple_leaf(__tuple_leaf const &) = default;
-    __tuple_leaf(__tuple_leaf &&) = default;
-
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    int
-    swap(__tuple_leaf& __t) _NOEXCEPT_(__is_nothrow_swappable<__tuple_leaf>::value)
-    {
-        _VSTD::swap(*this, __t);
-        return 0;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11       _Hp& get()       _NOEXCEPT {return static_cast<_Hp&>(*this);}
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return static_cast<const _Hp&>(*this);}
-};
-
-template <class ..._Tp>
-_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-void __swallow(_Tp&&...) _NOEXCEPT {}
-
-template <class _Tp>
-struct __all_default_constructible;
-
-template <class ..._Tp>
-struct __all_default_constructible<__tuple_types<_Tp...>>
-    : __all<is_default_constructible<_Tp>::value...>
-{ };
-
-// __tuple_impl
-
-template<class _Indx, class ..._Tp> struct __tuple_impl;
-
-template<size_t ..._Indx, class ..._Tp>
-struct _LIBCPP_DECLSPEC_EMPTY_BASES __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
-    : public __tuple_leaf<_Indx, _Tp>...
-{
-    _LIBCPP_INLINE_VISIBILITY
-    constexpr __tuple_impl()
-        _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
-
-    template <size_t ..._Uf, class ..._Tf,
-              size_t ..._Ul, class ..._Tl, class ..._Up>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        explicit
-        __tuple_impl(__tuple_indices<_Uf...>, __tuple_types<_Tf...>,
-                     __tuple_indices<_Ul...>, __tuple_types<_Tl...>,
-                     _Up&&... __u)
-                     _NOEXCEPT_((__all<is_nothrow_constructible<_Tf, _Up>::value...>::value &&
-                                 __all<is_nothrow_default_constructible<_Tl>::value...>::value)) :
-            __tuple_leaf<_Uf, _Tf>(_VSTD::forward<_Up>(__u))...,
-            __tuple_leaf<_Ul, _Tl>()...
-            {}
-
+                > 
+            > 
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value)) 
+            : _Hp(_VSTD::forward<_Tp>(__t)) {} 
+ 
+    template <class _Tp, class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY constexpr 
+        explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t) 
+            : _Hp(_VSTD::forward<_Tp>(__t)) {} 
+ 
+    template <class _Tp, class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY constexpr 
+        explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t) 
+            : _Hp(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t)) {} 
+ 
+    template <class _Tp, class _Alloc> 
+        _LIBCPP_INLINE_VISIBILITY constexpr 
+        explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t) 
+            : _Hp(_VSTD::forward<_Tp>(__t), __a) {} 
+ 
+    __tuple_leaf(__tuple_leaf const &) = default; 
+    __tuple_leaf(__tuple_leaf &&) = default; 
+ 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    int 
+    swap(__tuple_leaf& __t) _NOEXCEPT_(__is_nothrow_swappable<__tuple_leaf>::value) 
+    { 
+        _VSTD::swap(*this, __t); 
+        return 0; 
+    } 
+ 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11       _Hp& get()       _NOEXCEPT {return static_cast<_Hp&>(*this);} 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return static_cast<const _Hp&>(*this);} 
+}; 
+ 
+template <class ..._Tp> 
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+void __swallow(_Tp&&...) _NOEXCEPT {} 
+ 
+template <class _Tp> 
+struct __all_default_constructible; 
+ 
+template <class ..._Tp> 
+struct __all_default_constructible<__tuple_types<_Tp...>> 
+    : __all<is_default_constructible<_Tp>::value...> 
+{ }; 
+ 
+// __tuple_impl 
+ 
+template<class _Indx, class ..._Tp> struct __tuple_impl; 
+ 
+template<size_t ..._Indx, class ..._Tp> 
+struct _LIBCPP_DECLSPEC_EMPTY_BASES __tuple_impl<__tuple_indices<_Indx...>, _Tp...> 
+    : public __tuple_leaf<_Indx, _Tp>... 
+{ 
+    _LIBCPP_INLINE_VISIBILITY 
+    constexpr __tuple_impl() 
+        _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {} 
+ 
+    template <size_t ..._Uf, class ..._Tf, 
+              size_t ..._Ul, class ..._Tl, class ..._Up> 
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        explicit 
+        __tuple_impl(__tuple_indices<_Uf...>, __tuple_types<_Tf...>, 
+                     __tuple_indices<_Ul...>, __tuple_types<_Tl...>, 
+                     _Up&&... __u) 
+                     _NOEXCEPT_((__all<is_nothrow_constructible<_Tf, _Up>::value...>::value && 
+                                 __all<is_nothrow_default_constructible<_Tl>::value...>::value)) : 
+            __tuple_leaf<_Uf, _Tf>(_VSTD::forward<_Up>(__u))..., 
+            __tuple_leaf<_Ul, _Tl>()... 
+            {} 
+ 
 #if defined(__NVCC__) && defined(_LIBCPP_COMPILER_MSVC)
     // Yandex-specific: specialize the preceding constructor for the
     // case of empty _Ul and _Tl to work around nvcc+msvc bug
@@ -399,1195 +399,1195 @@ struct _LIBCPP_DECLSPEC_EMPTY_BASES __tuple_impl<__tuple_indices<_Indx...>, _Tp.
     // End of Yandex-specific
 #endif
 
-    template <class _Alloc, size_t ..._Uf, class ..._Tf,
-              size_t ..._Ul, class ..._Tl, class ..._Up>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        explicit
-        __tuple_impl(allocator_arg_t, const _Alloc& __a,
-                     __tuple_indices<_Uf...>, __tuple_types<_Tf...>,
-                     __tuple_indices<_Ul...>, __tuple_types<_Tl...>,
-                     _Up&&... __u) :
-            __tuple_leaf<_Uf, _Tf>(__uses_alloc_ctor<_Tf, _Alloc, _Up>(), __a,
-            _VSTD::forward<_Up>(__u))...,
-            __tuple_leaf<_Ul, _Tl>(__uses_alloc_ctor<_Tl, _Alloc>(), __a)...
-            {}
-
-    template <class _Tuple,
-              class = typename enable_if
-                      <
-                         __tuple_constructible<_Tuple, tuple<_Tp...> >::value
-                      >::type
-             >
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        __tuple_impl(_Tuple&& __t) _NOEXCEPT_((__all<is_nothrow_constructible<_Tp, typename tuple_element<_Indx,
-                                       typename __make_tuple_types<_Tuple>::type>::type>::value...>::value))
-            : __tuple_leaf<_Indx, _Tp>(_VSTD::forward<typename tuple_element<_Indx,
-                                       typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...
-            {}
-
-    template <class _Alloc, class _Tuple,
-              class = typename enable_if
-                      <
-                         __tuple_constructible<_Tuple, tuple<_Tp...> >::value
-                      >::type
-             >
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        __tuple_impl(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
-            : __tuple_leaf<_Indx, _Tp>(__uses_alloc_ctor<_Tp, _Alloc, typename tuple_element<_Indx,
-                                       typename __make_tuple_types<_Tuple>::type>::type>(), __a,
-                                       _VSTD::forward<typename tuple_element<_Indx,
-                                       typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...
-            {}
-
-    __tuple_impl(const __tuple_impl&) = default;
-    __tuple_impl(__tuple_impl&&) = default;
-
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    void swap(__tuple_impl& __t)
-        _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
-    {
-        _VSTD::__swallow(__tuple_leaf<_Indx, _Tp>::swap(static_cast<__tuple_leaf<_Indx, _Tp>&>(__t))...);
-    }
-};
-
-template<class _Dest, class _Source, size_t ..._Np>
-_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-void __memberwise_copy_assign(_Dest& __dest, _Source const& __source, __tuple_indices<_Np...>) {
-    _VSTD::__swallow(((_VSTD::get<_Np>(__dest) = _VSTD::get<_Np>(__source)), void(), 0)...);
-    }
-
-template<class _Dest, class _Source, class ..._Up, size_t ..._Np>
-_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-void __memberwise_forward_assign(_Dest& __dest, _Source&& __source, __tuple_types<_Up...>, __tuple_indices<_Np...>) {
-    _VSTD::__swallow(((
-        _VSTD::get<_Np>(__dest) = _VSTD::forward<_Up>(_VSTD::get<_Np>(__source))
-    ), void(), 0)...);
-    }
-
-template <class ..._Tp>
-class _LIBCPP_TEMPLATE_VIS tuple
-{
-    typedef __tuple_impl<typename __make_tuple_indices<sizeof...(_Tp)>::type, _Tp...> _BaseT;
-
-    _BaseT __base_;
-
-    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
-        typename tuple_element<_Jp, tuple<_Up...> >::type& get(tuple<_Up...>&) _NOEXCEPT;
-    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
-        const typename tuple_element<_Jp, tuple<_Up...> >::type& get(const tuple<_Up...>&) _NOEXCEPT;
-    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
-        typename tuple_element<_Jp, tuple<_Up...> >::type&& get(tuple<_Up...>&&) _NOEXCEPT;
-    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
-        const typename tuple_element<_Jp, tuple<_Up...> >::type&& get(const tuple<_Up...>&&) _NOEXCEPT;
-public:
-    // [tuple.cnstr]
-
-    // tuple() constructors (including allocator_arg_t variants)
-    template <template<class...> class _IsImpDefault = __is_implicitly_default_constructible, __enable_if_t<
-        _And<
-            _IsImpDefault<_Tp>... // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-    tuple()
-        _NOEXCEPT_(_And<is_nothrow_default_constructible<_Tp>...>::value)
-    { }
-
-    template <template<class...> class _IsImpDefault = __is_implicitly_default_constructible,
-              template<class...> class _IsDefault = is_default_constructible, __enable_if_t<
-        _And<
-            _IsDefault<_Tp>...,
-            _Not<_Lazy<_And, _IsImpDefault<_Tp>...> > // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-    explicit tuple()
-        _NOEXCEPT_(_And<is_nothrow_default_constructible<_Tp>...>::value)
-    { }
-
-    template <class _Alloc, template<class...> class _IsImpDefault = __is_implicitly_default_constructible, __enable_if_t<
-        _And<
-            _IsImpDefault<_Tp>... // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple(allocator_arg_t, _Alloc const& __a)
-      : __base_(allocator_arg_t(), __a,
-                    __tuple_indices<>(), __tuple_types<>(),
-                    typename __make_tuple_indices<sizeof...(_Tp), 0>::type(),
-                    __tuple_types<_Tp...>()) {}
-
-    template <class _Alloc,
-              template<class...> class _IsImpDefault = __is_implicitly_default_constructible,
-              template<class...> class _IsDefault = is_default_constructible, __enable_if_t<
-        _And<
-            _IsDefault<_Tp>...,
-            _Not<_Lazy<_And, _IsImpDefault<_Tp>...> > // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    explicit tuple(allocator_arg_t, _Alloc const& __a)
-      : __base_(allocator_arg_t(), __a,
-                    __tuple_indices<>(), __tuple_types<>(),
-                    typename __make_tuple_indices<sizeof...(_Tp), 0>::type(),
-                    __tuple_types<_Tp...>()) {}
-
-    // tuple(const T&...) constructors (including allocator_arg_t variants)
-    template <template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) >= 1>,
-            is_copy_constructible<_Tp>...,
-            is_convertible<const _Tp&, _Tp>... // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    tuple(const _Tp& ... __t)
-        _NOEXCEPT_(_And<is_nothrow_copy_constructible<_Tp>...>::value)
-        : __base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
-                typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
-                typename __make_tuple_indices<0>::type(),
-                typename __make_tuple_types<tuple, 0>::type(),
-                __t...
-               ) {}
-
-    template <template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) >= 1>,
-            is_copy_constructible<_Tp>...,
-            _Not<_Lazy<_And, is_convertible<const _Tp&, _Tp>...> > // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    explicit tuple(const _Tp& ... __t)
-        _NOEXCEPT_(_And<is_nothrow_copy_constructible<_Tp>...>::value)
-        : __base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
-                typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
-                typename __make_tuple_indices<0>::type(),
-                typename __make_tuple_types<tuple, 0>::type(),
-                __t...
-               ) {}
-
-    template <class _Alloc, template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) >= 1>,
-            is_copy_constructible<_Tp>...,
-            is_convertible<const _Tp&, _Tp>... // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t)
-        : __base_(allocator_arg_t(), __a,
-                typename __make_tuple_indices<sizeof...(_Tp)>::type(),
-                typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
-                typename __make_tuple_indices<0>::type(),
-                typename __make_tuple_types<tuple, 0>::type(),
-                __t...
-               ) {}
-
-    template <class _Alloc, template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) >= 1>,
-            is_copy_constructible<_Tp>...,
-            _Not<_Lazy<_And, is_convertible<const _Tp&, _Tp>...> > // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    explicit tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t)
-        : __base_(allocator_arg_t(), __a,
-                typename __make_tuple_indices<sizeof...(_Tp)>::type(),
-                typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
-                typename __make_tuple_indices<0>::type(),
-                typename __make_tuple_types<tuple, 0>::type(),
-                __t...
-               ) {}
-
-    // tuple(U&& ...) constructors (including allocator_arg_t variants)
-    template <class ..._Up> struct _IsThisTuple : false_type { };
-    template <class _Up> struct _IsThisTuple<_Up> : is_same<__uncvref_t<_Up>, tuple> { };
-
-    template <class ..._Up>
-    struct _EnableUTypesCtor : _And<
-        _BoolConstant<sizeof...(_Tp) >= 1>,
-        _Not<_IsThisTuple<_Up...> >, // extension to allow mis-behaved user constructors
-        is_constructible<_Tp, _Up>...
-    > { };
-
-    template <class ..._Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableUTypesCtor<_Up...>,
-            is_convertible<_Up, _Tp>... // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    tuple(_Up&&... __u)
-        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, _Up>...>::value))
-        : __base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
-                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
-                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
-                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
-                    _VSTD::forward<_Up>(__u)...) {}
-
-    template <class ..._Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableUTypesCtor<_Up...>,
-            _Not<_Lazy<_And, is_convertible<_Up, _Tp>...> > // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    explicit tuple(_Up&&... __u)
-        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, _Up>...>::value))
-        : __base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
-                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
-                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
-                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
-                    _VSTD::forward<_Up>(__u)...) {}
-
-    template <class _Alloc, class ..._Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableUTypesCtor<_Up...>,
-            is_convertible<_Up, _Tp>... // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u)
-        : __base_(allocator_arg_t(), __a,
-                    typename __make_tuple_indices<sizeof...(_Up)>::type(),
-                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
-                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
-                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
-                    _VSTD::forward<_Up>(__u)...) {}
-
-    template <class _Alloc, class ..._Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableUTypesCtor<_Up...>,
-            _Not<_Lazy<_And, is_convertible<_Up, _Tp>...> > // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    explicit tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u)
-        : __base_(allocator_arg_t(), __a,
-                    typename __make_tuple_indices<sizeof...(_Up)>::type(),
-                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
-                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
-                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
-                    _VSTD::forward<_Up>(__u)...) {}
-
-    // Copy and move constructors (including the allocator_arg_t variants)
-    tuple(const tuple&) = default;
-    tuple(tuple&&) = default;
-
-    template <class _Alloc, template<class...> class _And = _And, __enable_if_t<
-        _And<is_copy_constructible<_Tp>...>::value
-    , int> = 0>
-    tuple(allocator_arg_t, const _Alloc& __alloc, const tuple& __t)
-        : __base_(allocator_arg_t(), __alloc, __t)
-    { }
-
-    template <class _Alloc, template<class...> class _And = _And, __enable_if_t<
-        _And<is_move_constructible<_Tp>...>::value
-    , int> = 0>
-    tuple(allocator_arg_t, const _Alloc& __alloc, tuple&& __t)
-        : __base_(allocator_arg_t(), __alloc, _VSTD::move(__t))
-    { }
-
-    // tuple(const tuple<U...>&) constructors (including allocator_arg_t variants)
-    template <class ..._Up>
-    struct _EnableCopyFromOtherTuple : _And<
-        _Not<is_same<tuple<_Tp...>, tuple<_Up...> > >,
-        _Lazy<_Or,
-            _BoolConstant<sizeof...(_Tp) != 1>,
-            // _Tp and _Up are 1-element packs - the pack expansions look
-            // weird to avoid tripping up the type traits in degenerate cases
-            _Lazy<_And,
-                _Not<is_convertible<const tuple<_Up>&, _Tp> >...,
-                _Not<is_constructible<_Tp, const tuple<_Up>&> >...
-            >
-        >,
-        is_constructible<_Tp, const _Up&>...
-    > { };
-
-    template <class ..._Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableCopyFromOtherTuple<_Up...>,
-            is_convertible<const _Up&, _Tp>... // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    tuple(const tuple<_Up...>& __t)
-        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, const _Up&>...>::value))
-        : __base_(__t)
-    { }
-
-    template <class ..._Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableCopyFromOtherTuple<_Up...>,
-            _Not<_Lazy<_And, is_convertible<const _Up&, _Tp>...> > // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    explicit tuple(const tuple<_Up...>& __t)
-        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, const _Up&>...>::value))
-        : __base_(__t)
-    { }
-
-    template <class ..._Up, class _Alloc, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableCopyFromOtherTuple<_Up...>,
-            is_convertible<const _Up&, _Tp>... // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple(allocator_arg_t, const _Alloc& __a, const tuple<_Up...>& __t)
-        : __base_(allocator_arg_t(), __a, __t)
-    { }
-
-    template <class ..._Up, class _Alloc, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableCopyFromOtherTuple<_Up...>,
-            _Not<_Lazy<_And, is_convertible<const _Up&, _Tp>...> > // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    explicit tuple(allocator_arg_t, const _Alloc& __a, const tuple<_Up...>& __t)
-        : __base_(allocator_arg_t(), __a, __t)
-    { }
-
-    // tuple(tuple<U...>&&) constructors (including allocator_arg_t variants)
-    template <class ..._Up>
-    struct _EnableMoveFromOtherTuple : _And<
-        _Not<is_same<tuple<_Tp...>, tuple<_Up...> > >,
-        _Lazy<_Or,
-            _BoolConstant<sizeof...(_Tp) != 1>,
-            // _Tp and _Up are 1-element packs - the pack expansions look
-            // weird to avoid tripping up the type traits in degenerate cases
-            _Lazy<_And,
-                _Not<is_convertible<tuple<_Up>, _Tp> >...,
-                _Not<is_constructible<_Tp, tuple<_Up> > >...
-            >
-        >,
-        is_constructible<_Tp, _Up>...
-    > { };
-
-    template <class ..._Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableMoveFromOtherTuple<_Up...>,
-            is_convertible<_Up, _Tp>... // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    tuple(tuple<_Up...>&& __t)
-        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, _Up>...>::value))
-        : __base_(_VSTD::move(__t))
-    { }
-
-    template <class ..._Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableMoveFromOtherTuple<_Up...>,
-            _Not<_Lazy<_And, is_convertible<_Up, _Tp>...> > // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    explicit tuple(tuple<_Up...>&& __t)
-        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, _Up>...>::value))
-        : __base_(_VSTD::move(__t))
-    { }
-
-    template <class _Alloc, class ..._Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableMoveFromOtherTuple<_Up...>,
-            is_convertible<_Up, _Tp>... // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple(allocator_arg_t, const _Alloc& __a, tuple<_Up...>&& __t)
-        : __base_(allocator_arg_t(), __a, _VSTD::move(__t))
-    { }
-
-    template <class _Alloc, class ..._Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>,
-            _EnableMoveFromOtherTuple<_Up...>,
-            _Not<_Lazy<_And, is_convertible<_Up, _Tp>...> > // explicit check
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    explicit tuple(allocator_arg_t, const _Alloc& __a, tuple<_Up...>&& __t)
-        : __base_(allocator_arg_t(), __a, _VSTD::move(__t))
-    { }
-
-    // tuple(const pair<U1, U2>&) constructors (including allocator_arg_t variants)
-    template <class _Up1, class _Up2, class ..._DependentTp>
-    struct _EnableImplicitCopyFromPair : _And<
-        is_constructible<_FirstType<_DependentTp...>, const _Up1&>,
-        is_constructible<_SecondType<_DependentTp...>, const _Up2&>,
-        is_convertible<const _Up1&, _FirstType<_DependentTp...> >, // explicit check
-        is_convertible<const _Up2&, _SecondType<_DependentTp...> >
-    > { };
-
-    template <class _Up1, class _Up2, class ..._DependentTp>
-    struct _EnableExplicitCopyFromPair : _And<
-        is_constructible<_FirstType<_DependentTp...>, const _Up1&>,
-        is_constructible<_SecondType<_DependentTp...>, const _Up2&>,
-        _Not<is_convertible<const _Up1&, _FirstType<_DependentTp...> > >, // explicit check
-        _Not<is_convertible<const _Up2&, _SecondType<_DependentTp...> > >
-    > { };
-
-    template <class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) == 2>,
-            _EnableImplicitCopyFromPair<_Up1, _Up2, _Tp...>
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    tuple(const pair<_Up1, _Up2>& __p)
-        _NOEXCEPT_((_And<
-            is_nothrow_constructible<_FirstType<_Tp...>, const _Up1&>,
-            is_nothrow_constructible<_SecondType<_Tp...>, const _Up2&>
-        >::value))
-        : __base_(__p)
-    { }
-
-    template <class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) == 2>,
-            _EnableExplicitCopyFromPair<_Up1, _Up2, _Tp...>
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    explicit tuple(const pair<_Up1, _Up2>& __p)
-        _NOEXCEPT_((_And<
-            is_nothrow_constructible<_FirstType<_Tp...>, const _Up1&>,
-            is_nothrow_constructible<_SecondType<_Tp...>, const _Up2&>
-        >::value))
-        : __base_(__p)
-    { }
-
-    template <class _Alloc, class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) == 2>,
-            _EnableImplicitCopyFromPair<_Up1, _Up2, _Tp...>
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple(allocator_arg_t, const _Alloc& __a, const pair<_Up1, _Up2>& __p)
-        : __base_(allocator_arg_t(), __a, __p)
-    { }
-
-    template <class _Alloc, class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) == 2>,
-            _EnableExplicitCopyFromPair<_Up1, _Up2, _Tp...>
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    explicit tuple(allocator_arg_t, const _Alloc& __a, const pair<_Up1, _Up2>& __p)
-        : __base_(allocator_arg_t(), __a, __p)
-    { }
-
-    // tuple(pair<U1, U2>&&) constructors (including allocator_arg_t variants)
-    template <class _Up1, class _Up2, class ..._DependentTp>
-    struct _EnableImplicitMoveFromPair : _And<
-        is_constructible<_FirstType<_DependentTp...>, _Up1>,
-        is_constructible<_SecondType<_DependentTp...>, _Up2>,
-        is_convertible<_Up1, _FirstType<_DependentTp...> >, // explicit check
-        is_convertible<_Up2, _SecondType<_DependentTp...> >
-    > { };
-
-    template <class _Up1, class _Up2, class ..._DependentTp>
-    struct _EnableExplicitMoveFromPair : _And<
-        is_constructible<_FirstType<_DependentTp...>, _Up1>,
-        is_constructible<_SecondType<_DependentTp...>, _Up2>,
-        _Not<is_convertible<_Up1, _FirstType<_DependentTp...> > >, // explicit check
-        _Not<is_convertible<_Up2, _SecondType<_DependentTp...> > >
-    > { };
-
-    template <class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) == 2>,
-            _EnableImplicitMoveFromPair<_Up1, _Up2, _Tp...>
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    tuple(pair<_Up1, _Up2>&& __p)
-        _NOEXCEPT_((_And<
-            is_nothrow_constructible<_FirstType<_Tp...>, _Up1>,
-            is_nothrow_constructible<_SecondType<_Tp...>, _Up2>
-        >::value))
-        : __base_(_VSTD::move(__p))
-    { }
-
-    template <class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) == 2>,
-            _EnableExplicitMoveFromPair<_Up1, _Up2, _Tp...>
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    explicit tuple(pair<_Up1, _Up2>&& __p)
-        _NOEXCEPT_((_And<
-            is_nothrow_constructible<_FirstType<_Tp...>, _Up1>,
-            is_nothrow_constructible<_SecondType<_Tp...>, _Up2>
-        >::value))
-        : __base_(_VSTD::move(__p))
-    { }
-
-    template <class _Alloc, class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) == 2>,
-            _EnableImplicitMoveFromPair<_Up1, _Up2, _Tp...>
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple(allocator_arg_t, const _Alloc& __a, pair<_Up1, _Up2>&& __p)
-        : __base_(allocator_arg_t(), __a, _VSTD::move(__p))
-    { }
-
-    template <class _Alloc, class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) == 2>,
-            _EnableExplicitMoveFromPair<_Up1, _Up2, _Tp...>
-        >::value
-    , int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    explicit tuple(allocator_arg_t, const _Alloc& __a, pair<_Up1, _Up2>&& __p)
-        : __base_(allocator_arg_t(), __a, _VSTD::move(__p))
-    { }
-
-    // [tuple.assign]
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple& operator=(_If<_And<is_copy_assignable<_Tp>...>::value, tuple, __nat> const& __tuple)
-        _NOEXCEPT_((_And<is_nothrow_copy_assignable<_Tp>...>::value))
-    {
-        _VSTD::__memberwise_copy_assign(*this, __tuple,
-            typename __make_tuple_indices<sizeof...(_Tp)>::type());
-        return *this;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple& operator=(_If<_And<is_move_assignable<_Tp>...>::value, tuple, __nat>&& __tuple)
-        _NOEXCEPT_((_And<is_nothrow_move_assignable<_Tp>...>::value))
-    {
-        _VSTD::__memberwise_forward_assign(*this, _VSTD::move(__tuple),
-            __tuple_types<_Tp...>(),
-            typename __make_tuple_indices<sizeof...(_Tp)>::type());
-        return *this;
-    }
-
-    template<class... _Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) == sizeof...(_Up)>,
-            is_assignable<_Tp&, _Up const&>...
-        >::value
-    ,int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple& operator=(tuple<_Up...> const& __tuple)
-        _NOEXCEPT_((_And<is_nothrow_assignable<_Tp&, _Up const&>...>::value))
-    {
-        _VSTD::__memberwise_copy_assign(*this, __tuple,
-            typename __make_tuple_indices<sizeof...(_Tp)>::type());
-        return *this;
-    }
-
-    template<class... _Up, __enable_if_t<
-        _And<
-            _BoolConstant<sizeof...(_Tp) == sizeof...(_Up)>,
-            is_assignable<_Tp&, _Up>...
-        >::value
-    ,int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple& operator=(tuple<_Up...>&& __tuple)
-        _NOEXCEPT_((_And<is_nothrow_assignable<_Tp&, _Up>...>::value))
-    {
-        _VSTD::__memberwise_forward_assign(*this, _VSTD::move(__tuple),
-            __tuple_types<_Up...>(),
-            typename __make_tuple_indices<sizeof...(_Tp)>::type());
-        return *this;
-    }
-
-    template<class _Up1, class _Up2, class _Dep = true_type, __enable_if_t<
-        _And<_Dep,
-            _BoolConstant<sizeof...(_Tp) == 2>,
-            is_assignable<_FirstType<_Tp..., _Dep>&, _Up1 const&>,
-            is_assignable<_SecondType<_Tp..., _Dep>&, _Up2 const&>
-        >::value
-    ,int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple& operator=(pair<_Up1, _Up2> const& __pair)
-        _NOEXCEPT_((_And<
-            is_nothrow_assignable<_FirstType<_Tp...>&, _Up1 const&>,
-            is_nothrow_assignable<_SecondType<_Tp...>&, _Up2 const&>
-        >::value))
-    {
-        _VSTD::get<0>(*this) = __pair.first;
-        _VSTD::get<1>(*this) = __pair.second;
-        return *this;
-    }
-
-    template<class _Up1, class _Up2, class _Dep = true_type, __enable_if_t<
-        _And<_Dep,
-            _BoolConstant<sizeof...(_Tp) == 2>,
-            is_assignable<_FirstType<_Tp..., _Dep>&, _Up1>,
-            is_assignable<_SecondType<_Tp..., _Dep>&, _Up2>
-        >::value
-    ,int> = 0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple& operator=(pair<_Up1, _Up2>&& __pair)
-        _NOEXCEPT_((_And<
-            is_nothrow_assignable<_FirstType<_Tp...>&, _Up1>,
-            is_nothrow_assignable<_SecondType<_Tp...>&, _Up2>
-        >::value))
-    {
-        _VSTD::get<0>(*this) = _VSTD::forward<_Up1>(__pair.first);
-        _VSTD::get<1>(*this) = _VSTD::forward<_Up2>(__pair.second);
-        return *this;
-    }
-
-    // EXTENSION
-    template<class _Up, size_t _Np, class = __enable_if_t<
-        _And<
-            _BoolConstant<_Np == sizeof...(_Tp)>,
-            is_assignable<_Tp&, _Up const&>...
-        >::value
-    > >
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple& operator=(array<_Up, _Np> const& __array)
-        _NOEXCEPT_((_And<is_nothrow_assignable<_Tp&, _Up const&>...>::value))
-    {
-        _VSTD::__memberwise_copy_assign(*this, __array,
-            typename __make_tuple_indices<sizeof...(_Tp)>::type());
-        return *this;
-    }
-
-    // EXTENSION
-    template<class _Up, size_t _Np, class = void, class = __enable_if_t<
-        _And<
-            _BoolConstant<_Np == sizeof...(_Tp)>,
-            is_assignable<_Tp&, _Up>...
-        >::value
-    > >
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    tuple& operator=(array<_Up, _Np>&& __array)
-        _NOEXCEPT_((_And<is_nothrow_assignable<_Tp&, _Up>...>::value))
-    {
-        _VSTD::__memberwise_forward_assign(*this, _VSTD::move(__array),
-            __tuple_types<_If<true, _Up, _Tp>...>(),
-            typename __make_tuple_indices<sizeof...(_Tp)>::type());
-        return *this;
-    }
-
-    // [tuple.swap]
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    void swap(tuple& __t) _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
-        {__base_.swap(__t.__base_);}
-};
-
-template <>
-class _LIBCPP_TEMPLATE_VIS tuple<>
-{
-public:
-    _LIBCPP_INLINE_VISIBILITY constexpr
-        tuple() _NOEXCEPT = default;
-    template <class _Alloc>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-        tuple(allocator_arg_t, const _Alloc&) _NOEXCEPT {}
-    template <class _Alloc>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-        tuple(allocator_arg_t, const _Alloc&, const tuple&) _NOEXCEPT {}
-    template <class _Up>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-        tuple(array<_Up, 0>) _NOEXCEPT {}
-    template <class _Alloc, class _Up>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-        tuple(allocator_arg_t, const _Alloc&, array<_Up, 0>) _NOEXCEPT {}
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-    void swap(tuple&) _NOEXCEPT {}
-};
-
-#if _LIBCPP_STD_VER >= 17
-template <class ..._Tp>
-tuple(_Tp...) -> tuple<_Tp...>;
-template <class _Tp1, class _Tp2>
-tuple(pair<_Tp1, _Tp2>) -> tuple<_Tp1, _Tp2>;
-template <class _Alloc, class ..._Tp>
-tuple(allocator_arg_t, _Alloc, _Tp...) -> tuple<_Tp...>;
-template <class _Alloc, class _Tp1, class _Tp2>
-tuple(allocator_arg_t, _Alloc, pair<_Tp1, _Tp2>) -> tuple<_Tp1, _Tp2>;
-template <class _Alloc, class ..._Tp>
-tuple(allocator_arg_t, _Alloc, tuple<_Tp...>) -> tuple<_Tp...>;
-#endif
-
-template <class ..._Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-typename enable_if
-<
-    __all<__is_swappable<_Tp>::value...>::value,
-    void
->::type
-swap(tuple<_Tp...>& __t, tuple<_Tp...>& __u)
-                 _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
-    {__t.swap(__u);}
-
-// get
-
-template <size_t _Ip, class ..._Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-typename tuple_element<_Ip, tuple<_Tp...> >::type&
-get(tuple<_Tp...>& __t) _NOEXCEPT
-{
-    typedef _LIBCPP_NODEBUG typename tuple_element<_Ip, tuple<_Tp...> >::type type;
-    return static_cast<__tuple_leaf<_Ip, type>&>(__t.__base_).get();
-}
-
-template <size_t _Ip, class ..._Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-const typename tuple_element<_Ip, tuple<_Tp...> >::type&
-get(const tuple<_Tp...>& __t) _NOEXCEPT
-{
-    typedef _LIBCPP_NODEBUG typename tuple_element<_Ip, tuple<_Tp...> >::type type;
-    return static_cast<const __tuple_leaf<_Ip, type>&>(__t.__base_).get();
-}
-
-template <size_t _Ip, class ..._Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-typename tuple_element<_Ip, tuple<_Tp...> >::type&&
-get(tuple<_Tp...>&& __t) _NOEXCEPT
-{
-    typedef _LIBCPP_NODEBUG typename tuple_element<_Ip, tuple<_Tp...> >::type type;
-    return static_cast<type&&>(
-             static_cast<__tuple_leaf<_Ip, type>&&>(__t.__base_).get());
-}
-
-template <size_t _Ip, class ..._Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-const typename tuple_element<_Ip, tuple<_Tp...> >::type&&
-get(const tuple<_Tp...>&& __t) _NOEXCEPT
-{
-    typedef _LIBCPP_NODEBUG typename tuple_element<_Ip, tuple<_Tp...> >::type type;
-    return static_cast<const type&&>(
-             static_cast<const __tuple_leaf<_Ip, type>&&>(__t.__base_).get());
-}
-
-#if _LIBCPP_STD_VER > 11
-
-namespace __find_detail {
-
-static constexpr size_t __not_found = static_cast<size_t>(-1);
-static constexpr size_t __ambiguous = __not_found - 1;
-
-inline _LIBCPP_INLINE_VISIBILITY
-constexpr size_t __find_idx_return(size_t __curr_i, size_t __res, bool __matches) {
-    return !__matches ? __res :
-        (__res == __not_found ? __curr_i : __ambiguous);
-}
-
-template <size_t _Nx>
-inline _LIBCPP_INLINE_VISIBILITY
-constexpr size_t __find_idx(size_t __i, const bool (&__matches)[_Nx]) {
-  return __i == _Nx ? __not_found :
-      __find_idx_return(__i, __find_idx(__i + 1, __matches), __matches[__i]);
-}
-
-template <class _T1, class ..._Args>
-struct __find_exactly_one_checked {
-    static constexpr bool __matches[sizeof...(_Args)] = {is_same<_T1, _Args>::value...};
-    static constexpr size_t value = __find_detail::__find_idx(0, __matches);
+    template <class _Alloc, size_t ..._Uf, class ..._Tf, 
+              size_t ..._Ul, class ..._Tl, class ..._Up> 
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        explicit 
+        __tuple_impl(allocator_arg_t, const _Alloc& __a, 
+                     __tuple_indices<_Uf...>, __tuple_types<_Tf...>, 
+                     __tuple_indices<_Ul...>, __tuple_types<_Tl...>, 
+                     _Up&&... __u) : 
+            __tuple_leaf<_Uf, _Tf>(__uses_alloc_ctor<_Tf, _Alloc, _Up>(), __a, 
+            _VSTD::forward<_Up>(__u))..., 
+            __tuple_leaf<_Ul, _Tl>(__uses_alloc_ctor<_Tl, _Alloc>(), __a)... 
+            {} 
+ 
+    template <class _Tuple, 
+              class = typename enable_if 
+                      < 
+                         __tuple_constructible<_Tuple, tuple<_Tp...> >::value 
+                      >::type 
+             > 
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        __tuple_impl(_Tuple&& __t) _NOEXCEPT_((__all<is_nothrow_constructible<_Tp, typename tuple_element<_Indx, 
+                                       typename __make_tuple_types<_Tuple>::type>::type>::value...>::value)) 
+            : __tuple_leaf<_Indx, _Tp>(_VSTD::forward<typename tuple_element<_Indx, 
+                                       typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))... 
+            {} 
+ 
+    template <class _Alloc, class _Tuple, 
+              class = typename enable_if 
+                      < 
+                         __tuple_constructible<_Tuple, tuple<_Tp...> >::value 
+                      >::type 
+             > 
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        __tuple_impl(allocator_arg_t, const _Alloc& __a, _Tuple&& __t) 
+            : __tuple_leaf<_Indx, _Tp>(__uses_alloc_ctor<_Tp, _Alloc, typename tuple_element<_Indx, 
+                                       typename __make_tuple_types<_Tuple>::type>::type>(), __a, 
+                                       _VSTD::forward<typename tuple_element<_Indx, 
+                                       typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))... 
+            {} 
+ 
+    __tuple_impl(const __tuple_impl&) = default; 
+    __tuple_impl(__tuple_impl&&) = default; 
+ 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    void swap(__tuple_impl& __t) 
+        _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value) 
+    { 
+        _VSTD::__swallow(__tuple_leaf<_Indx, _Tp>::swap(static_cast<__tuple_leaf<_Indx, _Tp>&>(__t))...); 
+    } 
+}; 
+ 
+template<class _Dest, class _Source, size_t ..._Np> 
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+void __memberwise_copy_assign(_Dest& __dest, _Source const& __source, __tuple_indices<_Np...>) { 
+    _VSTD::__swallow(((_VSTD::get<_Np>(__dest) = _VSTD::get<_Np>(__source)), void(), 0)...); 
+    } 
+ 
+template<class _Dest, class _Source, class ..._Up, size_t ..._Np> 
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+void __memberwise_forward_assign(_Dest& __dest, _Source&& __source, __tuple_types<_Up...>, __tuple_indices<_Np...>) { 
+    _VSTD::__swallow((( 
+        _VSTD::get<_Np>(__dest) = _VSTD::forward<_Up>(_VSTD::get<_Np>(__source)) 
+    ), void(), 0)...); 
+    } 
+ 
+template <class ..._Tp> 
+class _LIBCPP_TEMPLATE_VIS tuple 
+{ 
+    typedef __tuple_impl<typename __make_tuple_indices<sizeof...(_Tp)>::type, _Tp...> _BaseT; 
+ 
+    _BaseT __base_; 
+ 
+    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        typename tuple_element<_Jp, tuple<_Up...> >::type& get(tuple<_Up...>&) _NOEXCEPT; 
+    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        const typename tuple_element<_Jp, tuple<_Up...> >::type& get(const tuple<_Up...>&) _NOEXCEPT; 
+    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        typename tuple_element<_Jp, tuple<_Up...> >::type&& get(tuple<_Up...>&&) _NOEXCEPT; 
+    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11 
+        const typename tuple_element<_Jp, tuple<_Up...> >::type&& get(const tuple<_Up...>&&) _NOEXCEPT; 
+public: 
+    // [tuple.cnstr] 
+ 
+    // tuple() constructors (including allocator_arg_t variants) 
+    template <template<class...> class _IsImpDefault = __is_implicitly_default_constructible, __enable_if_t< 
+        _And< 
+            _IsImpDefault<_Tp>... // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 
+    tuple() 
+        _NOEXCEPT_(_And<is_nothrow_default_constructible<_Tp>...>::value) 
+    { } 
+ 
+    template <template<class...> class _IsImpDefault = __is_implicitly_default_constructible, 
+              template<class...> class _IsDefault = is_default_constructible, __enable_if_t< 
+        _And< 
+            _IsDefault<_Tp>..., 
+            _Not<_Lazy<_And, _IsImpDefault<_Tp>...> > // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 
+    explicit tuple() 
+        _NOEXCEPT_(_And<is_nothrow_default_constructible<_Tp>...>::value) 
+    { } 
+ 
+    template <class _Alloc, template<class...> class _IsImpDefault = __is_implicitly_default_constructible, __enable_if_t< 
+        _And< 
+            _IsImpDefault<_Tp>... // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple(allocator_arg_t, _Alloc const& __a) 
+      : __base_(allocator_arg_t(), __a, 
+                    __tuple_indices<>(), __tuple_types<>(), 
+                    typename __make_tuple_indices<sizeof...(_Tp), 0>::type(), 
+                    __tuple_types<_Tp...>()) {} 
+ 
+    template <class _Alloc, 
+              template<class...> class _IsImpDefault = __is_implicitly_default_constructible, 
+              template<class...> class _IsDefault = is_default_constructible, __enable_if_t< 
+        _And< 
+            _IsDefault<_Tp>..., 
+            _Not<_Lazy<_And, _IsImpDefault<_Tp>...> > // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    explicit tuple(allocator_arg_t, _Alloc const& __a) 
+      : __base_(allocator_arg_t(), __a, 
+                    __tuple_indices<>(), __tuple_types<>(), 
+                    typename __make_tuple_indices<sizeof...(_Tp), 0>::type(), 
+                    __tuple_types<_Tp...>()) {} 
+ 
+    // tuple(const T&...) constructors (including allocator_arg_t variants) 
+    template <template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) >= 1>, 
+            is_copy_constructible<_Tp>..., 
+            is_convertible<const _Tp&, _Tp>... // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    tuple(const _Tp& ... __t) 
+        _NOEXCEPT_(_And<is_nothrow_copy_constructible<_Tp>...>::value) 
+        : __base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(), 
+                typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(), 
+                typename __make_tuple_indices<0>::type(), 
+                typename __make_tuple_types<tuple, 0>::type(), 
+                __t... 
+               ) {} 
+ 
+    template <template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) >= 1>, 
+            is_copy_constructible<_Tp>..., 
+            _Not<_Lazy<_And, is_convertible<const _Tp&, _Tp>...> > // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    explicit tuple(const _Tp& ... __t) 
+        _NOEXCEPT_(_And<is_nothrow_copy_constructible<_Tp>...>::value) 
+        : __base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(), 
+                typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(), 
+                typename __make_tuple_indices<0>::type(), 
+                typename __make_tuple_types<tuple, 0>::type(), 
+                __t... 
+               ) {} 
+ 
+    template <class _Alloc, template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) >= 1>, 
+            is_copy_constructible<_Tp>..., 
+            is_convertible<const _Tp&, _Tp>... // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t) 
+        : __base_(allocator_arg_t(), __a, 
+                typename __make_tuple_indices<sizeof...(_Tp)>::type(), 
+                typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(), 
+                typename __make_tuple_indices<0>::type(), 
+                typename __make_tuple_types<tuple, 0>::type(), 
+                __t... 
+               ) {} 
+ 
+    template <class _Alloc, template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) >= 1>, 
+            is_copy_constructible<_Tp>..., 
+            _Not<_Lazy<_And, is_convertible<const _Tp&, _Tp>...> > // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    explicit tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t) 
+        : __base_(allocator_arg_t(), __a, 
+                typename __make_tuple_indices<sizeof...(_Tp)>::type(), 
+                typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(), 
+                typename __make_tuple_indices<0>::type(), 
+                typename __make_tuple_types<tuple, 0>::type(), 
+                __t... 
+               ) {} 
+ 
+    // tuple(U&& ...) constructors (including allocator_arg_t variants) 
+    template <class ..._Up> struct _IsThisTuple : false_type { }; 
+    template <class _Up> struct _IsThisTuple<_Up> : is_same<__uncvref_t<_Up>, tuple> { }; 
+ 
+    template <class ..._Up> 
+    struct _EnableUTypesCtor : _And< 
+        _BoolConstant<sizeof...(_Tp) >= 1>, 
+        _Not<_IsThisTuple<_Up...> >, // extension to allow mis-behaved user constructors 
+        is_constructible<_Tp, _Up>... 
+    > { }; 
+ 
+    template <class ..._Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableUTypesCtor<_Up...>, 
+            is_convertible<_Up, _Tp>... // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    tuple(_Up&&... __u) 
+        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, _Up>...>::value)) 
+        : __base_(typename __make_tuple_indices<sizeof...(_Up)>::type(), 
+                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(), 
+                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(), 
+                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(), 
+                    _VSTD::forward<_Up>(__u)...) {} 
+ 
+    template <class ..._Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableUTypesCtor<_Up...>, 
+            _Not<_Lazy<_And, is_convertible<_Up, _Tp>...> > // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    explicit tuple(_Up&&... __u) 
+        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, _Up>...>::value)) 
+        : __base_(typename __make_tuple_indices<sizeof...(_Up)>::type(), 
+                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(), 
+                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(), 
+                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(), 
+                    _VSTD::forward<_Up>(__u)...) {} 
+ 
+    template <class _Alloc, class ..._Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableUTypesCtor<_Up...>, 
+            is_convertible<_Up, _Tp>... // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u) 
+        : __base_(allocator_arg_t(), __a, 
+                    typename __make_tuple_indices<sizeof...(_Up)>::type(), 
+                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(), 
+                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(), 
+                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(), 
+                    _VSTD::forward<_Up>(__u)...) {} 
+ 
+    template <class _Alloc, class ..._Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableUTypesCtor<_Up...>, 
+            _Not<_Lazy<_And, is_convertible<_Up, _Tp>...> > // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    explicit tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u) 
+        : __base_(allocator_arg_t(), __a, 
+                    typename __make_tuple_indices<sizeof...(_Up)>::type(), 
+                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(), 
+                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(), 
+                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(), 
+                    _VSTD::forward<_Up>(__u)...) {} 
+ 
+    // Copy and move constructors (including the allocator_arg_t variants) 
+    tuple(const tuple&) = default; 
+    tuple(tuple&&) = default; 
+ 
+    template <class _Alloc, template<class...> class _And = _And, __enable_if_t< 
+        _And<is_copy_constructible<_Tp>...>::value 
+    , int> = 0> 
+    tuple(allocator_arg_t, const _Alloc& __alloc, const tuple& __t) 
+        : __base_(allocator_arg_t(), __alloc, __t) 
+    { } 
+ 
+    template <class _Alloc, template<class...> class _And = _And, __enable_if_t< 
+        _And<is_move_constructible<_Tp>...>::value 
+    , int> = 0> 
+    tuple(allocator_arg_t, const _Alloc& __alloc, tuple&& __t) 
+        : __base_(allocator_arg_t(), __alloc, _VSTD::move(__t)) 
+    { } 
+ 
+    // tuple(const tuple<U...>&) constructors (including allocator_arg_t variants) 
+    template <class ..._Up> 
+    struct _EnableCopyFromOtherTuple : _And< 
+        _Not<is_same<tuple<_Tp...>, tuple<_Up...> > >, 
+        _Lazy<_Or, 
+            _BoolConstant<sizeof...(_Tp) != 1>, 
+            // _Tp and _Up are 1-element packs - the pack expansions look 
+            // weird to avoid tripping up the type traits in degenerate cases 
+            _Lazy<_And, 
+                _Not<is_convertible<const tuple<_Up>&, _Tp> >..., 
+                _Not<is_constructible<_Tp, const tuple<_Up>&> >... 
+            > 
+        >, 
+        is_constructible<_Tp, const _Up&>... 
+    > { }; 
+ 
+    template <class ..._Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableCopyFromOtherTuple<_Up...>, 
+            is_convertible<const _Up&, _Tp>... // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    tuple(const tuple<_Up...>& __t) 
+        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, const _Up&>...>::value)) 
+        : __base_(__t) 
+    { } 
+ 
+    template <class ..._Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableCopyFromOtherTuple<_Up...>, 
+            _Not<_Lazy<_And, is_convertible<const _Up&, _Tp>...> > // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    explicit tuple(const tuple<_Up...>& __t) 
+        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, const _Up&>...>::value)) 
+        : __base_(__t) 
+    { } 
+ 
+    template <class ..._Up, class _Alloc, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableCopyFromOtherTuple<_Up...>, 
+            is_convertible<const _Up&, _Tp>... // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple(allocator_arg_t, const _Alloc& __a, const tuple<_Up...>& __t) 
+        : __base_(allocator_arg_t(), __a, __t) 
+    { } 
+ 
+    template <class ..._Up, class _Alloc, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableCopyFromOtherTuple<_Up...>, 
+            _Not<_Lazy<_And, is_convertible<const _Up&, _Tp>...> > // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    explicit tuple(allocator_arg_t, const _Alloc& __a, const tuple<_Up...>& __t) 
+        : __base_(allocator_arg_t(), __a, __t) 
+    { } 
+ 
+    // tuple(tuple<U...>&&) constructors (including allocator_arg_t variants) 
+    template <class ..._Up> 
+    struct _EnableMoveFromOtherTuple : _And< 
+        _Not<is_same<tuple<_Tp...>, tuple<_Up...> > >, 
+        _Lazy<_Or, 
+            _BoolConstant<sizeof...(_Tp) != 1>, 
+            // _Tp and _Up are 1-element packs - the pack expansions look 
+            // weird to avoid tripping up the type traits in degenerate cases 
+            _Lazy<_And, 
+                _Not<is_convertible<tuple<_Up>, _Tp> >..., 
+                _Not<is_constructible<_Tp, tuple<_Up> > >... 
+            > 
+        >, 
+        is_constructible<_Tp, _Up>... 
+    > { }; 
+ 
+    template <class ..._Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableMoveFromOtherTuple<_Up...>, 
+            is_convertible<_Up, _Tp>... // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    tuple(tuple<_Up...>&& __t) 
+        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, _Up>...>::value)) 
+        : __base_(_VSTD::move(__t)) 
+    { } 
+ 
+    template <class ..._Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableMoveFromOtherTuple<_Up...>, 
+            _Not<_Lazy<_And, is_convertible<_Up, _Tp>...> > // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    explicit tuple(tuple<_Up...>&& __t) 
+        _NOEXCEPT_((_And<is_nothrow_constructible<_Tp, _Up>...>::value)) 
+        : __base_(_VSTD::move(__t)) 
+    { } 
+ 
+    template <class _Alloc, class ..._Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableMoveFromOtherTuple<_Up...>, 
+            is_convertible<_Up, _Tp>... // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple(allocator_arg_t, const _Alloc& __a, tuple<_Up...>&& __t) 
+        : __base_(allocator_arg_t(), __a, _VSTD::move(__t)) 
+    { } 
+ 
+    template <class _Alloc, class ..._Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, 
+            _EnableMoveFromOtherTuple<_Up...>, 
+            _Not<_Lazy<_And, is_convertible<_Up, _Tp>...> > // explicit check 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    explicit tuple(allocator_arg_t, const _Alloc& __a, tuple<_Up...>&& __t) 
+        : __base_(allocator_arg_t(), __a, _VSTD::move(__t)) 
+    { } 
+ 
+    // tuple(const pair<U1, U2>&) constructors (including allocator_arg_t variants) 
+    template <class _Up1, class _Up2, class ..._DependentTp> 
+    struct _EnableImplicitCopyFromPair : _And< 
+        is_constructible<_FirstType<_DependentTp...>, const _Up1&>, 
+        is_constructible<_SecondType<_DependentTp...>, const _Up2&>, 
+        is_convertible<const _Up1&, _FirstType<_DependentTp...> >, // explicit check 
+        is_convertible<const _Up2&, _SecondType<_DependentTp...> > 
+    > { }; 
+ 
+    template <class _Up1, class _Up2, class ..._DependentTp> 
+    struct _EnableExplicitCopyFromPair : _And< 
+        is_constructible<_FirstType<_DependentTp...>, const _Up1&>, 
+        is_constructible<_SecondType<_DependentTp...>, const _Up2&>, 
+        _Not<is_convertible<const _Up1&, _FirstType<_DependentTp...> > >, // explicit check 
+        _Not<is_convertible<const _Up2&, _SecondType<_DependentTp...> > > 
+    > { }; 
+ 
+    template <class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) == 2>, 
+            _EnableImplicitCopyFromPair<_Up1, _Up2, _Tp...> 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    tuple(const pair<_Up1, _Up2>& __p) 
+        _NOEXCEPT_((_And< 
+            is_nothrow_constructible<_FirstType<_Tp...>, const _Up1&>, 
+            is_nothrow_constructible<_SecondType<_Tp...>, const _Up2&> 
+        >::value)) 
+        : __base_(__p) 
+    { } 
+ 
+    template <class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) == 2>, 
+            _EnableExplicitCopyFromPair<_Up1, _Up2, _Tp...> 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    explicit tuple(const pair<_Up1, _Up2>& __p) 
+        _NOEXCEPT_((_And< 
+            is_nothrow_constructible<_FirstType<_Tp...>, const _Up1&>, 
+            is_nothrow_constructible<_SecondType<_Tp...>, const _Up2&> 
+        >::value)) 
+        : __base_(__p) 
+    { } 
+ 
+    template <class _Alloc, class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) == 2>, 
+            _EnableImplicitCopyFromPair<_Up1, _Up2, _Tp...> 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple(allocator_arg_t, const _Alloc& __a, const pair<_Up1, _Up2>& __p) 
+        : __base_(allocator_arg_t(), __a, __p) 
+    { } 
+ 
+    template <class _Alloc, class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) == 2>, 
+            _EnableExplicitCopyFromPair<_Up1, _Up2, _Tp...> 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    explicit tuple(allocator_arg_t, const _Alloc& __a, const pair<_Up1, _Up2>& __p) 
+        : __base_(allocator_arg_t(), __a, __p) 
+    { } 
+ 
+    // tuple(pair<U1, U2>&&) constructors (including allocator_arg_t variants) 
+    template <class _Up1, class _Up2, class ..._DependentTp> 
+    struct _EnableImplicitMoveFromPair : _And< 
+        is_constructible<_FirstType<_DependentTp...>, _Up1>, 
+        is_constructible<_SecondType<_DependentTp...>, _Up2>, 
+        is_convertible<_Up1, _FirstType<_DependentTp...> >, // explicit check 
+        is_convertible<_Up2, _SecondType<_DependentTp...> > 
+    > { }; 
+ 
+    template <class _Up1, class _Up2, class ..._DependentTp> 
+    struct _EnableExplicitMoveFromPair : _And< 
+        is_constructible<_FirstType<_DependentTp...>, _Up1>, 
+        is_constructible<_SecondType<_DependentTp...>, _Up2>, 
+        _Not<is_convertible<_Up1, _FirstType<_DependentTp...> > >, // explicit check 
+        _Not<is_convertible<_Up2, _SecondType<_DependentTp...> > > 
+    > { }; 
+ 
+    template <class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) == 2>, 
+            _EnableImplicitMoveFromPair<_Up1, _Up2, _Tp...> 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    tuple(pair<_Up1, _Up2>&& __p) 
+        _NOEXCEPT_((_And< 
+            is_nothrow_constructible<_FirstType<_Tp...>, _Up1>, 
+            is_nothrow_constructible<_SecondType<_Tp...>, _Up2> 
+        >::value)) 
+        : __base_(_VSTD::move(__p)) 
+    { } 
+ 
+    template <class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) == 2>, 
+            _EnableExplicitMoveFromPair<_Up1, _Up2, _Tp...> 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    explicit tuple(pair<_Up1, _Up2>&& __p) 
+        _NOEXCEPT_((_And< 
+            is_nothrow_constructible<_FirstType<_Tp...>, _Up1>, 
+            is_nothrow_constructible<_SecondType<_Tp...>, _Up2> 
+        >::value)) 
+        : __base_(_VSTD::move(__p)) 
+    { } 
+ 
+    template <class _Alloc, class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) == 2>, 
+            _EnableImplicitMoveFromPair<_Up1, _Up2, _Tp...> 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple(allocator_arg_t, const _Alloc& __a, pair<_Up1, _Up2>&& __p) 
+        : __base_(allocator_arg_t(), __a, _VSTD::move(__p)) 
+    { } 
+ 
+    template <class _Alloc, class _Up1, class _Up2, template<class...> class _And = _And, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) == 2>, 
+            _EnableExplicitMoveFromPair<_Up1, _Up2, _Tp...> 
+        >::value 
+    , int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    explicit tuple(allocator_arg_t, const _Alloc& __a, pair<_Up1, _Up2>&& __p) 
+        : __base_(allocator_arg_t(), __a, _VSTD::move(__p)) 
+    { } 
+ 
+    // [tuple.assign] 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple& operator=(_If<_And<is_copy_assignable<_Tp>...>::value, tuple, __nat> const& __tuple) 
+        _NOEXCEPT_((_And<is_nothrow_copy_assignable<_Tp>...>::value)) 
+    { 
+        _VSTD::__memberwise_copy_assign(*this, __tuple, 
+            typename __make_tuple_indices<sizeof...(_Tp)>::type()); 
+        return *this; 
+    } 
+ 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple& operator=(_If<_And<is_move_assignable<_Tp>...>::value, tuple, __nat>&& __tuple) 
+        _NOEXCEPT_((_And<is_nothrow_move_assignable<_Tp>...>::value)) 
+    { 
+        _VSTD::__memberwise_forward_assign(*this, _VSTD::move(__tuple), 
+            __tuple_types<_Tp...>(), 
+            typename __make_tuple_indices<sizeof...(_Tp)>::type()); 
+        return *this; 
+    } 
+ 
+    template<class... _Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) == sizeof...(_Up)>, 
+            is_assignable<_Tp&, _Up const&>... 
+        >::value 
+    ,int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple& operator=(tuple<_Up...> const& __tuple) 
+        _NOEXCEPT_((_And<is_nothrow_assignable<_Tp&, _Up const&>...>::value)) 
+    { 
+        _VSTD::__memberwise_copy_assign(*this, __tuple, 
+            typename __make_tuple_indices<sizeof...(_Tp)>::type()); 
+        return *this; 
+    } 
+ 
+    template<class... _Up, __enable_if_t< 
+        _And< 
+            _BoolConstant<sizeof...(_Tp) == sizeof...(_Up)>, 
+            is_assignable<_Tp&, _Up>... 
+        >::value 
+    ,int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple& operator=(tuple<_Up...>&& __tuple) 
+        _NOEXCEPT_((_And<is_nothrow_assignable<_Tp&, _Up>...>::value)) 
+    { 
+        _VSTD::__memberwise_forward_assign(*this, _VSTD::move(__tuple), 
+            __tuple_types<_Up...>(), 
+            typename __make_tuple_indices<sizeof...(_Tp)>::type()); 
+        return *this; 
+    } 
+ 
+    template<class _Up1, class _Up2, class _Dep = true_type, __enable_if_t< 
+        _And<_Dep, 
+            _BoolConstant<sizeof...(_Tp) == 2>, 
+            is_assignable<_FirstType<_Tp..., _Dep>&, _Up1 const&>, 
+            is_assignable<_SecondType<_Tp..., _Dep>&, _Up2 const&> 
+        >::value 
+    ,int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple& operator=(pair<_Up1, _Up2> const& __pair) 
+        _NOEXCEPT_((_And< 
+            is_nothrow_assignable<_FirstType<_Tp...>&, _Up1 const&>, 
+            is_nothrow_assignable<_SecondType<_Tp...>&, _Up2 const&> 
+        >::value)) 
+    { 
+        _VSTD::get<0>(*this) = __pair.first; 
+        _VSTD::get<1>(*this) = __pair.second; 
+        return *this; 
+    } 
+ 
+    template<class _Up1, class _Up2, class _Dep = true_type, __enable_if_t< 
+        _And<_Dep, 
+            _BoolConstant<sizeof...(_Tp) == 2>, 
+            is_assignable<_FirstType<_Tp..., _Dep>&, _Up1>, 
+            is_assignable<_SecondType<_Tp..., _Dep>&, _Up2> 
+        >::value 
+    ,int> = 0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple& operator=(pair<_Up1, _Up2>&& __pair) 
+        _NOEXCEPT_((_And< 
+            is_nothrow_assignable<_FirstType<_Tp...>&, _Up1>, 
+            is_nothrow_assignable<_SecondType<_Tp...>&, _Up2> 
+        >::value)) 
+    { 
+        _VSTD::get<0>(*this) = _VSTD::forward<_Up1>(__pair.first); 
+        _VSTD::get<1>(*this) = _VSTD::forward<_Up2>(__pair.second); 
+        return *this; 
+    } 
+ 
+    // EXTENSION 
+    template<class _Up, size_t _Np, class = __enable_if_t< 
+        _And< 
+            _BoolConstant<_Np == sizeof...(_Tp)>, 
+            is_assignable<_Tp&, _Up const&>... 
+        >::value 
+    > > 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple& operator=(array<_Up, _Np> const& __array) 
+        _NOEXCEPT_((_And<is_nothrow_assignable<_Tp&, _Up const&>...>::value)) 
+    { 
+        _VSTD::__memberwise_copy_assign(*this, __array, 
+            typename __make_tuple_indices<sizeof...(_Tp)>::type()); 
+        return *this; 
+    } 
+ 
+    // EXTENSION 
+    template<class _Up, size_t _Np, class = void, class = __enable_if_t< 
+        _And< 
+            _BoolConstant<_Np == sizeof...(_Tp)>, 
+            is_assignable<_Tp&, _Up>... 
+        >::value 
+    > > 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    tuple& operator=(array<_Up, _Np>&& __array) 
+        _NOEXCEPT_((_And<is_nothrow_assignable<_Tp&, _Up>...>::value)) 
+    { 
+        _VSTD::__memberwise_forward_assign(*this, _VSTD::move(__array), 
+            __tuple_types<_If<true, _Up, _Tp>...>(), 
+            typename __make_tuple_indices<sizeof...(_Tp)>::type()); 
+        return *this; 
+    } 
+ 
+    // [tuple.swap] 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    void swap(tuple& __t) _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value) 
+        {__base_.swap(__t.__base_);} 
+}; 
+ 
+template <> 
+class _LIBCPP_TEMPLATE_VIS tuple<> 
+{ 
+public: 
+    _LIBCPP_INLINE_VISIBILITY constexpr 
+        tuple() _NOEXCEPT = default; 
+    template <class _Alloc> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+        tuple(allocator_arg_t, const _Alloc&) _NOEXCEPT {} 
+    template <class _Alloc> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+        tuple(allocator_arg_t, const _Alloc&, const tuple&) _NOEXCEPT {} 
+    template <class _Up> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+        tuple(array<_Up, 0>) _NOEXCEPT {} 
+    template <class _Alloc, class _Up> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+        tuple(allocator_arg_t, const _Alloc&, array<_Up, 0>) _NOEXCEPT {} 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+    void swap(tuple&) _NOEXCEPT {} 
+}; 
+ 
+#if _LIBCPP_STD_VER >= 17 
+template <class ..._Tp> 
+tuple(_Tp...) -> tuple<_Tp...>; 
+template <class _Tp1, class _Tp2> 
+tuple(pair<_Tp1, _Tp2>) -> tuple<_Tp1, _Tp2>; 
+template <class _Alloc, class ..._Tp> 
+tuple(allocator_arg_t, _Alloc, _Tp...) -> tuple<_Tp...>; 
+template <class _Alloc, class _Tp1, class _Tp2> 
+tuple(allocator_arg_t, _Alloc, pair<_Tp1, _Tp2>) -> tuple<_Tp1, _Tp2>; 
+template <class _Alloc, class ..._Tp> 
+tuple(allocator_arg_t, _Alloc, tuple<_Tp...>) -> tuple<_Tp...>; 
+#endif 
+ 
+template <class ..._Tp> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+typename enable_if 
+< 
+    __all<__is_swappable<_Tp>::value...>::value, 
+    void 
+>::type 
+swap(tuple<_Tp...>& __t, tuple<_Tp...>& __u) 
+                 _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value) 
+    {__t.swap(__u);} 
+ 
+// get 
+ 
+template <size_t _Ip, class ..._Tp> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+typename tuple_element<_Ip, tuple<_Tp...> >::type& 
+get(tuple<_Tp...>& __t) _NOEXCEPT 
+{ 
+    typedef _LIBCPP_NODEBUG typename tuple_element<_Ip, tuple<_Tp...> >::type type; 
+    return static_cast<__tuple_leaf<_Ip, type>&>(__t.__base_).get(); 
+} 
+ 
+template <size_t _Ip, class ..._Tp> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+const typename tuple_element<_Ip, tuple<_Tp...> >::type& 
+get(const tuple<_Tp...>& __t) _NOEXCEPT 
+{ 
+    typedef _LIBCPP_NODEBUG typename tuple_element<_Ip, tuple<_Tp...> >::type type; 
+    return static_cast<const __tuple_leaf<_Ip, type>&>(__t.__base_).get(); 
+} 
+ 
+template <size_t _Ip, class ..._Tp> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+typename tuple_element<_Ip, tuple<_Tp...> >::type&& 
+get(tuple<_Tp...>&& __t) _NOEXCEPT 
+{ 
+    typedef _LIBCPP_NODEBUG typename tuple_element<_Ip, tuple<_Tp...> >::type type; 
+    return static_cast<type&&>( 
+             static_cast<__tuple_leaf<_Ip, type>&&>(__t.__base_).get()); 
+} 
+ 
+template <size_t _Ip, class ..._Tp> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+const typename tuple_element<_Ip, tuple<_Tp...> >::type&& 
+get(const tuple<_Tp...>&& __t) _NOEXCEPT 
+{ 
+    typedef _LIBCPP_NODEBUG typename tuple_element<_Ip, tuple<_Tp...> >::type type; 
+    return static_cast<const type&&>( 
+             static_cast<const __tuple_leaf<_Ip, type>&&>(__t.__base_).get()); 
+} 
+ 
+#if _LIBCPP_STD_VER > 11 
+ 
+namespace __find_detail { 
+ 
+static constexpr size_t __not_found = static_cast<size_t>(-1); 
+static constexpr size_t __ambiguous = __not_found - 1; 
+ 
+inline _LIBCPP_INLINE_VISIBILITY 
+constexpr size_t __find_idx_return(size_t __curr_i, size_t __res, bool __matches) { 
+    return !__matches ? __res : 
+        (__res == __not_found ? __curr_i : __ambiguous); 
+} 
+ 
+template <size_t _Nx> 
+inline _LIBCPP_INLINE_VISIBILITY 
+constexpr size_t __find_idx(size_t __i, const bool (&__matches)[_Nx]) { 
+  return __i == _Nx ? __not_found : 
+      __find_idx_return(__i, __find_idx(__i + 1, __matches), __matches[__i]); 
+} 
+ 
+template <class _T1, class ..._Args> 
+struct __find_exactly_one_checked { 
+    static constexpr bool __matches[sizeof...(_Args)] = {is_same<_T1, _Args>::value...}; 
+    static constexpr size_t value = __find_detail::__find_idx(0, __matches); 
     static_assert(value != __not_found, "type not found in type list" );
     static_assert(value != __ambiguous, "type occurs more than once in type list");
-};
-
-template <class _T1>
-struct __find_exactly_one_checked<_T1> {
-    static_assert(!is_same<_T1, _T1>::value, "type not in empty type list");
-};
-
-} // namespace __find_detail;
-
-template <typename _T1, typename... _Args>
-struct __find_exactly_one_t
-    : public __find_detail::__find_exactly_one_checked<_T1, _Args...> {
-};
-
-template <class _T1, class... _Args>
-inline _LIBCPP_INLINE_VISIBILITY
-constexpr _T1& get(tuple<_Args...>& __tup) noexcept
-{
-    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(__tup);
-}
-
-template <class _T1, class... _Args>
-inline _LIBCPP_INLINE_VISIBILITY
-constexpr _T1 const& get(tuple<_Args...> const& __tup) noexcept
-{
-    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(__tup);
-}
-
-template <class _T1, class... _Args>
-inline _LIBCPP_INLINE_VISIBILITY
-constexpr _T1&& get(tuple<_Args...>&& __tup) noexcept
-{
-    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(_VSTD::move(__tup));
-}
-
-template <class _T1, class... _Args>
-inline _LIBCPP_INLINE_VISIBILITY
-constexpr _T1 const&& get(tuple<_Args...> const&& __tup) noexcept
-{
-    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(_VSTD::move(__tup));
-}
-
-#endif
-
-// tie
-
-template <class ..._Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-tuple<_Tp&...>
-tie(_Tp&... __t) _NOEXCEPT
-{
-    return tuple<_Tp&...>(__t...);
-}
-
-template <class _Up>
-struct __ignore_t
-{
-    template <class _Tp>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    const __ignore_t& operator=(_Tp&&) const {return *this;}
-};
-
-namespace {
-  constexpr __ignore_t<unsigned char> ignore = __ignore_t<unsigned char>();
-}
-
-template <class... _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+}; 
+ 
+template <class _T1> 
+struct __find_exactly_one_checked<_T1> { 
+    static_assert(!is_same<_T1, _T1>::value, "type not in empty type list"); 
+}; 
+ 
+} // namespace __find_detail; 
+ 
+template <typename _T1, typename... _Args> 
+struct __find_exactly_one_t 
+    : public __find_detail::__find_exactly_one_checked<_T1, _Args...> { 
+}; 
+ 
+template <class _T1, class... _Args> 
+inline _LIBCPP_INLINE_VISIBILITY 
+constexpr _T1& get(tuple<_Args...>& __tup) noexcept 
+{ 
+    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(__tup); 
+} 
+ 
+template <class _T1, class... _Args> 
+inline _LIBCPP_INLINE_VISIBILITY 
+constexpr _T1 const& get(tuple<_Args...> const& __tup) noexcept 
+{ 
+    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(__tup); 
+} 
+ 
+template <class _T1, class... _Args> 
+inline _LIBCPP_INLINE_VISIBILITY 
+constexpr _T1&& get(tuple<_Args...>&& __tup) noexcept 
+{ 
+    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(_VSTD::move(__tup)); 
+} 
+ 
+template <class _T1, class... _Args> 
+inline _LIBCPP_INLINE_VISIBILITY 
+constexpr _T1 const&& get(tuple<_Args...> const&& __tup) noexcept 
+{ 
+    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(_VSTD::move(__tup)); 
+} 
+ 
+#endif 
+ 
+// tie 
+ 
+template <class ..._Tp> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+tuple<_Tp&...> 
+tie(_Tp&... __t) _NOEXCEPT 
+{ 
+    return tuple<_Tp&...>(__t...); 
+} 
+ 
+template <class _Up> 
+struct __ignore_t 
+{ 
+    template <class _Tp> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    const __ignore_t& operator=(_Tp&&) const {return *this;} 
+}; 
+ 
+namespace { 
+  constexpr __ignore_t<unsigned char> ignore = __ignore_t<unsigned char>(); 
+} 
+ 
+template <class... _Tp> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
 tuple<typename __unwrap_ref_decay<_Tp>::type...>
-make_tuple(_Tp&&... __t)
-{
+make_tuple(_Tp&&... __t) 
+{ 
     return tuple<typename __unwrap_ref_decay<_Tp>::type...>(_VSTD::forward<_Tp>(__t)...);
-}
-
-template <class... _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-tuple<_Tp&&...>
-forward_as_tuple(_Tp&&... __t) _NOEXCEPT
-{
-    return tuple<_Tp&&...>(_VSTD::forward<_Tp>(__t)...);
-}
-
-template <size_t _Ip>
-struct __tuple_equal
-{
-    template <class _Tp, class _Up>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    bool operator()(const _Tp& __x, const _Up& __y)
-    {
-        return __tuple_equal<_Ip - 1>()(__x, __y) && _VSTD::get<_Ip-1>(__x) == _VSTD::get<_Ip-1>(__y);
-    }
-};
-
-template <>
-struct __tuple_equal<0>
-{
-    template <class _Tp, class _Up>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    bool operator()(const _Tp&, const _Up&)
-    {
-        return true;
-    }
-};
-
-template <class ..._Tp, class ..._Up>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-bool
-operator==(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
-{
-    static_assert (sizeof...(_Tp) == sizeof...(_Up), "Can't compare tuples of different sizes");
-    return __tuple_equal<sizeof...(_Tp)>()(__x, __y);
-}
-
-template <class ..._Tp, class ..._Up>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-bool
-operator!=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
-{
-    return !(__x == __y);
-}
-
-template <size_t _Ip>
-struct __tuple_less
-{
-    template <class _Tp, class _Up>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    bool operator()(const _Tp& __x, const _Up& __y)
-    {
-        const size_t __idx = tuple_size<_Tp>::value - _Ip;
-        if (_VSTD::get<__idx>(__x) < _VSTD::get<__idx>(__y))
-            return true;
-        if (_VSTD::get<__idx>(__y) < _VSTD::get<__idx>(__x))
-            return false;
-        return __tuple_less<_Ip-1>()(__x, __y);
-    }
-};
-
-template <>
-struct __tuple_less<0>
-{
-    template <class _Tp, class _Up>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    bool operator()(const _Tp&, const _Up&)
-    {
-        return false;
-    }
-};
-
-template <class ..._Tp, class ..._Up>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-bool
-operator<(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
-{
-    static_assert (sizeof...(_Tp) == sizeof...(_Up), "Can't compare tuples of different sizes");
-    return __tuple_less<sizeof...(_Tp)>()(__x, __y);
-}
-
-template <class ..._Tp, class ..._Up>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-bool
-operator>(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
-{
-    return __y < __x;
-}
-
-template <class ..._Tp, class ..._Up>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-bool
-operator>=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
-{
-    return !(__x < __y);
-}
-
-template <class ..._Tp, class ..._Up>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-bool
-operator<=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
-{
-    return !(__y < __x);
-}
-
-// tuple_cat
-
-template <class _Tp, class _Up> struct __tuple_cat_type;
-
-template <class ..._Ttypes, class ..._Utypes>
-struct __tuple_cat_type<tuple<_Ttypes...>, __tuple_types<_Utypes...> >
-{
-    typedef _LIBCPP_NODEBUG tuple<_Ttypes..., _Utypes...> type;
-};
-
-template <class _ResultTuple, bool _Is_Tuple0TupleLike, class ..._Tuples>
-struct __tuple_cat_return_1
-{
-};
-
-template <class ..._Types, class _Tuple0>
-struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0>
-{
-    typedef _LIBCPP_NODEBUG typename __tuple_cat_type<tuple<_Types...>,
-            typename __make_tuple_types<typename __uncvref<_Tuple0>::type>::type>::type
-                                                                           type;
-};
-
-template <class ..._Types, class _Tuple0, class _Tuple1, class ..._Tuples>
-struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0, _Tuple1, _Tuples...>
-    : public __tuple_cat_return_1<
-                 typename __tuple_cat_type<
-                     tuple<_Types...>,
-                     typename __make_tuple_types<typename __uncvref<_Tuple0>::type>::type
-                 >::type,
-                 __tuple_like<typename remove_reference<_Tuple1>::type>::value,
-                 _Tuple1, _Tuples...>
-{
-};
-
-template <class ..._Tuples> struct __tuple_cat_return;
-
-template <class _Tuple0, class ..._Tuples>
-struct __tuple_cat_return<_Tuple0, _Tuples...>
-    : public __tuple_cat_return_1<tuple<>,
-         __tuple_like<typename remove_reference<_Tuple0>::type>::value, _Tuple0,
-                                                                     _Tuples...>
-{
-};
-
-template <>
-struct __tuple_cat_return<>
-{
-    typedef _LIBCPP_NODEBUG tuple<> type;
-};
-
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-tuple<>
-tuple_cat()
-{
-    return tuple<>();
-}
-
-template <class _Rp, class _Indices, class _Tuple0, class ..._Tuples>
-struct __tuple_cat_return_ref_imp;
-
-template <class ..._Types, size_t ..._I0, class _Tuple0>
-struct __tuple_cat_return_ref_imp<tuple<_Types...>, __tuple_indices<_I0...>, _Tuple0>
-{
-    typedef _LIBCPP_NODEBUG typename remove_reference<_Tuple0>::type _T0;
-    typedef tuple<_Types..., typename __apply_cv<_Tuple0,
-                          typename tuple_element<_I0, _T0>::type>::type&&...> type;
-};
-
-template <class ..._Types, size_t ..._I0, class _Tuple0, class _Tuple1, class ..._Tuples>
-struct __tuple_cat_return_ref_imp<tuple<_Types...>, __tuple_indices<_I0...>,
-                                  _Tuple0, _Tuple1, _Tuples...>
-    : public __tuple_cat_return_ref_imp<
-         tuple<_Types..., typename __apply_cv<_Tuple0,
-               typename tuple_element<_I0,
-                  typename remove_reference<_Tuple0>::type>::type>::type&&...>,
-         typename __make_tuple_indices<tuple_size<typename
-                                 remove_reference<_Tuple1>::type>::value>::type,
-         _Tuple1, _Tuples...>
-{
-};
-
-template <class _Tuple0, class ..._Tuples>
-struct __tuple_cat_return_ref
-    : public __tuple_cat_return_ref_imp<tuple<>,
-               typename __make_tuple_indices<
-                        tuple_size<typename remove_reference<_Tuple0>::type>::value
-               >::type, _Tuple0, _Tuples...>
-{
-};
-
-template <class _Types, class _I0, class _J0>
-struct __tuple_cat;
-
-template <class ..._Types, size_t ..._I0, size_t ..._J0>
-struct __tuple_cat<tuple<_Types...>, __tuple_indices<_I0...>, __tuple_indices<_J0...> >
-{
-    template <class _Tuple0>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&>::type
-    operator()(tuple<_Types...> __t, _Tuple0&& __t0)
-    {
-        return _VSTD::forward_as_tuple(
-            _VSTD::forward<_Types>(_VSTD::get<_I0>(__t))...,
+} 
+ 
+template <class... _Tp> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+tuple<_Tp&&...> 
+forward_as_tuple(_Tp&&... __t) _NOEXCEPT 
+{ 
+    return tuple<_Tp&&...>(_VSTD::forward<_Tp>(__t)...); 
+} 
+ 
+template <size_t _Ip> 
+struct __tuple_equal 
+{ 
+    template <class _Tp, class _Up> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    bool operator()(const _Tp& __x, const _Up& __y) 
+    { 
+        return __tuple_equal<_Ip - 1>()(__x, __y) && _VSTD::get<_Ip-1>(__x) == _VSTD::get<_Ip-1>(__y); 
+    } 
+}; 
+ 
+template <> 
+struct __tuple_equal<0> 
+{ 
+    template <class _Tp, class _Up> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    bool operator()(const _Tp&, const _Up&) 
+    { 
+        return true; 
+    } 
+}; 
+ 
+template <class ..._Tp, class ..._Up> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+bool 
+operator==(const tuple<_Tp...>& __x, const tuple<_Up...>& __y) 
+{ 
+    static_assert (sizeof...(_Tp) == sizeof...(_Up), "Can't compare tuples of different sizes"); 
+    return __tuple_equal<sizeof...(_Tp)>()(__x, __y); 
+} 
+ 
+template <class ..._Tp, class ..._Up> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+bool 
+operator!=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y) 
+{ 
+    return !(__x == __y); 
+} 
+ 
+template <size_t _Ip> 
+struct __tuple_less 
+{ 
+    template <class _Tp, class _Up> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    bool operator()(const _Tp& __x, const _Up& __y) 
+    { 
+        const size_t __idx = tuple_size<_Tp>::value - _Ip; 
+        if (_VSTD::get<__idx>(__x) < _VSTD::get<__idx>(__y)) 
+            return true; 
+        if (_VSTD::get<__idx>(__y) < _VSTD::get<__idx>(__x)) 
+            return false; 
+        return __tuple_less<_Ip-1>()(__x, __y); 
+    } 
+}; 
+ 
+template <> 
+struct __tuple_less<0> 
+{ 
+    template <class _Tp, class _Up> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    bool operator()(const _Tp&, const _Up&) 
+    { 
+        return false; 
+    } 
+}; 
+ 
+template <class ..._Tp, class ..._Up> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+bool 
+operator<(const tuple<_Tp...>& __x, const tuple<_Up...>& __y) 
+{ 
+    static_assert (sizeof...(_Tp) == sizeof...(_Up), "Can't compare tuples of different sizes"); 
+    return __tuple_less<sizeof...(_Tp)>()(__x, __y); 
+} 
+ 
+template <class ..._Tp, class ..._Up> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+bool 
+operator>(const tuple<_Tp...>& __x, const tuple<_Up...>& __y) 
+{ 
+    return __y < __x; 
+} 
+ 
+template <class ..._Tp, class ..._Up> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+bool 
+operator>=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y) 
+{ 
+    return !(__x < __y); 
+} 
+ 
+template <class ..._Tp, class ..._Up> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+bool 
+operator<=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y) 
+{ 
+    return !(__y < __x); 
+} 
+ 
+// tuple_cat 
+ 
+template <class _Tp, class _Up> struct __tuple_cat_type; 
+ 
+template <class ..._Ttypes, class ..._Utypes> 
+struct __tuple_cat_type<tuple<_Ttypes...>, __tuple_types<_Utypes...> > 
+{ 
+    typedef _LIBCPP_NODEBUG tuple<_Ttypes..., _Utypes...> type; 
+}; 
+ 
+template <class _ResultTuple, bool _Is_Tuple0TupleLike, class ..._Tuples> 
+struct __tuple_cat_return_1 
+{ 
+}; 
+ 
+template <class ..._Types, class _Tuple0> 
+struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0> 
+{ 
+    typedef _LIBCPP_NODEBUG typename __tuple_cat_type<tuple<_Types...>, 
+            typename __make_tuple_types<typename __uncvref<_Tuple0>::type>::type>::type 
+                                                                           type; 
+}; 
+ 
+template <class ..._Types, class _Tuple0, class _Tuple1, class ..._Tuples> 
+struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0, _Tuple1, _Tuples...> 
+    : public __tuple_cat_return_1< 
+                 typename __tuple_cat_type< 
+                     tuple<_Types...>, 
+                     typename __make_tuple_types<typename __uncvref<_Tuple0>::type>::type 
+                 >::type, 
+                 __tuple_like<typename remove_reference<_Tuple1>::type>::value, 
+                 _Tuple1, _Tuples...> 
+{ 
+}; 
+ 
+template <class ..._Tuples> struct __tuple_cat_return; 
+ 
+template <class _Tuple0, class ..._Tuples> 
+struct __tuple_cat_return<_Tuple0, _Tuples...> 
+    : public __tuple_cat_return_1<tuple<>, 
+         __tuple_like<typename remove_reference<_Tuple0>::type>::value, _Tuple0, 
+                                                                     _Tuples...> 
+{ 
+}; 
+ 
+template <> 
+struct __tuple_cat_return<> 
+{ 
+    typedef _LIBCPP_NODEBUG tuple<> type; 
+}; 
+ 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+tuple<> 
+tuple_cat() 
+{ 
+    return tuple<>(); 
+} 
+ 
+template <class _Rp, class _Indices, class _Tuple0, class ..._Tuples> 
+struct __tuple_cat_return_ref_imp; 
+ 
+template <class ..._Types, size_t ..._I0, class _Tuple0> 
+struct __tuple_cat_return_ref_imp<tuple<_Types...>, __tuple_indices<_I0...>, _Tuple0> 
+{ 
+    typedef _LIBCPP_NODEBUG typename remove_reference<_Tuple0>::type _T0; 
+    typedef tuple<_Types..., typename __apply_cv<_Tuple0, 
+                          typename tuple_element<_I0, _T0>::type>::type&&...> type; 
+}; 
+ 
+template <class ..._Types, size_t ..._I0, class _Tuple0, class _Tuple1, class ..._Tuples> 
+struct __tuple_cat_return_ref_imp<tuple<_Types...>, __tuple_indices<_I0...>, 
+                                  _Tuple0, _Tuple1, _Tuples...> 
+    : public __tuple_cat_return_ref_imp< 
+         tuple<_Types..., typename __apply_cv<_Tuple0, 
+               typename tuple_element<_I0, 
+                  typename remove_reference<_Tuple0>::type>::type>::type&&...>, 
+         typename __make_tuple_indices<tuple_size<typename 
+                                 remove_reference<_Tuple1>::type>::value>::type, 
+         _Tuple1, _Tuples...> 
+{ 
+}; 
+ 
+template <class _Tuple0, class ..._Tuples> 
+struct __tuple_cat_return_ref 
+    : public __tuple_cat_return_ref_imp<tuple<>, 
+               typename __make_tuple_indices< 
+                        tuple_size<typename remove_reference<_Tuple0>::type>::value 
+               >::type, _Tuple0, _Tuples...> 
+{ 
+}; 
+ 
+template <class _Types, class _I0, class _J0> 
+struct __tuple_cat; 
+ 
+template <class ..._Types, size_t ..._I0, size_t ..._J0> 
+struct __tuple_cat<tuple<_Types...>, __tuple_indices<_I0...>, __tuple_indices<_J0...> > 
+{ 
+    template <class _Tuple0> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&>::type 
+    operator()(tuple<_Types...> __t, _Tuple0&& __t0) 
+    { 
+        return _VSTD::forward_as_tuple( 
+            _VSTD::forward<_Types>(_VSTD::get<_I0>(__t))..., 
             _VSTD::get<_J0>(_VSTD::forward<_Tuple0>(__t0))...);
-    }
-
-    template <class _Tuple0, class _Tuple1, class ..._Tuples>
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&, _Tuple1&&, _Tuples&&...>::type
-    operator()(tuple<_Types...> __t, _Tuple0&& __t0, _Tuple1&& __t1, _Tuples&& ...__tpls)
-    {
-        typedef _LIBCPP_NODEBUG typename remove_reference<_Tuple0>::type _T0;
-        typedef _LIBCPP_NODEBUG typename remove_reference<_Tuple1>::type _T1;
-        return __tuple_cat<
-            tuple<_Types...,
-                  typename __apply_cv<_Tuple0, typename tuple_element<
-                                                   _J0, _T0>::type>::type&&...>,
-            typename __make_tuple_indices<sizeof...(_Types) +
-                                          tuple_size<_T0>::value>::type,
-            typename __make_tuple_indices<tuple_size<_T1>::value>::type>()(
-            _VSTD::forward_as_tuple(
+    } 
+ 
+    template <class _Tuple0, class _Tuple1, class ..._Tuples> 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&, _Tuple1&&, _Tuples&&...>::type 
+    operator()(tuple<_Types...> __t, _Tuple0&& __t0, _Tuple1&& __t1, _Tuples&& ...__tpls) 
+    { 
+        typedef _LIBCPP_NODEBUG typename remove_reference<_Tuple0>::type _T0; 
+        typedef _LIBCPP_NODEBUG typename remove_reference<_Tuple1>::type _T1; 
+        return __tuple_cat< 
+            tuple<_Types..., 
+                  typename __apply_cv<_Tuple0, typename tuple_element< 
+                                                   _J0, _T0>::type>::type&&...>, 
+            typename __make_tuple_indices<sizeof...(_Types) + 
+                                          tuple_size<_T0>::value>::type, 
+            typename __make_tuple_indices<tuple_size<_T1>::value>::type>()( 
+            _VSTD::forward_as_tuple( 
                 _VSTD::forward<_Types>(_VSTD::get<_I0>(__t))...,
-                _VSTD::get<_J0>(_VSTD::forward<_Tuple0>(__t0))...),
-            _VSTD::forward<_Tuple1>(__t1), _VSTD::forward<_Tuples>(__tpls)...);
-    }
-};
-
-template <class _Tuple0, class... _Tuples>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-typename __tuple_cat_return<_Tuple0, _Tuples...>::type
-tuple_cat(_Tuple0&& __t0, _Tuples&&... __tpls)
-{
-    typedef _LIBCPP_NODEBUG typename remove_reference<_Tuple0>::type _T0;
-    return __tuple_cat<tuple<>, __tuple_indices<>,
-                  typename __make_tuple_indices<tuple_size<_T0>::value>::type>()
-                  (tuple<>(), _VSTD::forward<_Tuple0>(__t0),
-                                            _VSTD::forward<_Tuples>(__tpls)...);
-}
-
-template <class ..._Tp, class _Alloc>
-struct _LIBCPP_TEMPLATE_VIS uses_allocator<tuple<_Tp...>, _Alloc>
-    : true_type {};
-
-template <class _T1, class _T2>
-template <class... _Args1, class... _Args2, size_t ..._I1, size_t ..._I2>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-pair<_T1, _T2>::pair(piecewise_construct_t,
-                     tuple<_Args1...>& __first_args, tuple<_Args2...>& __second_args,
-                     __tuple_indices<_I1...>, __tuple_indices<_I2...>)
-    :  first(_VSTD::forward<_Args1>(_VSTD::get<_I1>( __first_args))...),
-      second(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
-{
+                _VSTD::get<_J0>(_VSTD::forward<_Tuple0>(__t0))...), 
+            _VSTD::forward<_Tuple1>(__t1), _VSTD::forward<_Tuples>(__tpls)...); 
+    } 
+}; 
+ 
+template <class _Tuple0, class... _Tuples> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+typename __tuple_cat_return<_Tuple0, _Tuples...>::type 
+tuple_cat(_Tuple0&& __t0, _Tuples&&... __tpls) 
+{ 
+    typedef _LIBCPP_NODEBUG typename remove_reference<_Tuple0>::type _T0; 
+    return __tuple_cat<tuple<>, __tuple_indices<>, 
+                  typename __make_tuple_indices<tuple_size<_T0>::value>::type>() 
+                  (tuple<>(), _VSTD::forward<_Tuple0>(__t0), 
+                                            _VSTD::forward<_Tuples>(__tpls)...); 
+} 
+ 
+template <class ..._Tp, class _Alloc> 
+struct _LIBCPP_TEMPLATE_VIS uses_allocator<tuple<_Tp...>, _Alloc> 
+    : true_type {}; 
+ 
+template <class _T1, class _T2> 
+template <class... _Args1, class... _Args2, size_t ..._I1, size_t ..._I2> 
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 
+pair<_T1, _T2>::pair(piecewise_construct_t, 
+                     tuple<_Args1...>& __first_args, tuple<_Args2...>& __second_args, 
+                     __tuple_indices<_I1...>, __tuple_indices<_I2...>) 
+    :  first(_VSTD::forward<_Args1>(_VSTD::get<_I1>( __first_args))...), 
+      second(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...) 
+{ 
     (void)__first_args;
     (void)__second_args;
-}
-
-#if _LIBCPP_STD_VER > 14
-template <class _Tp>
-inline constexpr size_t tuple_size_v = tuple_size<_Tp>::value;
-
-#define _LIBCPP_NOEXCEPT_RETURN(...) noexcept(noexcept(__VA_ARGS__)) { return __VA_ARGS__; }
-
-template <class _Fn, class _Tuple, size_t ..._Id>
-inline _LIBCPP_INLINE_VISIBILITY
-constexpr decltype(auto) __apply_tuple_impl(_Fn && __f, _Tuple && __t,
-                                            __tuple_indices<_Id...>)
-_LIBCPP_NOEXCEPT_RETURN(
-    _VSTD::__invoke_constexpr(
-        _VSTD::forward<_Fn>(__f),
-        _VSTD::get<_Id>(_VSTD::forward<_Tuple>(__t))...)
-)
-
-template <class _Fn, class _Tuple>
-inline _LIBCPP_INLINE_VISIBILITY
-constexpr decltype(auto) apply(_Fn && __f, _Tuple && __t)
-_LIBCPP_NOEXCEPT_RETURN(
-    _VSTD::__apply_tuple_impl(
-        _VSTD::forward<_Fn>(__f), _VSTD::forward<_Tuple>(__t),
-        typename __make_tuple_indices<tuple_size_v<remove_reference_t<_Tuple>>>::type{})
-)
-
-template <class _Tp, class _Tuple, size_t... _Idx>
-inline _LIBCPP_INLINE_VISIBILITY
-constexpr _Tp __make_from_tuple_impl(_Tuple&& __t, __tuple_indices<_Idx...>)
-_LIBCPP_NOEXCEPT_RETURN(
-    _Tp(_VSTD::get<_Idx>(_VSTD::forward<_Tuple>(__t))...)
-)
-
-template <class _Tp, class _Tuple>
-inline _LIBCPP_INLINE_VISIBILITY
-constexpr _Tp make_from_tuple(_Tuple&& __t)
-_LIBCPP_NOEXCEPT_RETURN(
-    _VSTD::__make_from_tuple_impl<_Tp>(_VSTD::forward<_Tuple>(__t),
-        typename __make_tuple_indices<tuple_size_v<remove_reference_t<_Tuple>>>::type{})
-)
-
-#undef _LIBCPP_NOEXCEPT_RETURN
-
-#endif // _LIBCPP_STD_VER > 14
-
-#endif // !defined(_LIBCPP_CXX03_LANG)
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // _LIBCPP_TUPLE
+} 
+ 
+#if _LIBCPP_STD_VER > 14 
+template <class _Tp> 
+inline constexpr size_t tuple_size_v = tuple_size<_Tp>::value; 
+ 
+#define _LIBCPP_NOEXCEPT_RETURN(...) noexcept(noexcept(__VA_ARGS__)) { return __VA_ARGS__; } 
+ 
+template <class _Fn, class _Tuple, size_t ..._Id> 
+inline _LIBCPP_INLINE_VISIBILITY 
+constexpr decltype(auto) __apply_tuple_impl(_Fn && __f, _Tuple && __t, 
+                                            __tuple_indices<_Id...>) 
+_LIBCPP_NOEXCEPT_RETURN( 
+    _VSTD::__invoke_constexpr( 
+        _VSTD::forward<_Fn>(__f), 
+        _VSTD::get<_Id>(_VSTD::forward<_Tuple>(__t))...) 
+) 
+ 
+template <class _Fn, class _Tuple> 
+inline _LIBCPP_INLINE_VISIBILITY 
+constexpr decltype(auto) apply(_Fn && __f, _Tuple && __t) 
+_LIBCPP_NOEXCEPT_RETURN( 
+    _VSTD::__apply_tuple_impl( 
+        _VSTD::forward<_Fn>(__f), _VSTD::forward<_Tuple>(__t), 
+        typename __make_tuple_indices<tuple_size_v<remove_reference_t<_Tuple>>>::type{}) 
+) 
+ 
+template <class _Tp, class _Tuple, size_t... _Idx> 
+inline _LIBCPP_INLINE_VISIBILITY 
+constexpr _Tp __make_from_tuple_impl(_Tuple&& __t, __tuple_indices<_Idx...>) 
+_LIBCPP_NOEXCEPT_RETURN( 
+    _Tp(_VSTD::get<_Idx>(_VSTD::forward<_Tuple>(__t))...) 
+) 
+ 
+template <class _Tp, class _Tuple> 
+inline _LIBCPP_INLINE_VISIBILITY 
+constexpr _Tp make_from_tuple(_Tuple&& __t) 
+_LIBCPP_NOEXCEPT_RETURN( 
+    _VSTD::__make_from_tuple_impl<_Tp>(_VSTD::forward<_Tuple>(__t), 
+        typename __make_tuple_indices<tuple_size_v<remove_reference_t<_Tuple>>>::type{}) 
+) 
+ 
+#undef _LIBCPP_NOEXCEPT_RETURN 
+ 
+#endif // _LIBCPP_STD_VER > 14 
+ 
+#endif // !defined(_LIBCPP_CXX03_LANG) 
+ 
+_LIBCPP_END_NAMESPACE_STD 
+ 
+#endif // _LIBCPP_TUPLE