1 files changed, 107 insertions, 0 deletions
diff --git a/libcxx/include/__iterator/iter_swap.h b/libcxx/include/__iterator/iter_swap.h
new file mode 100644
index 000000000000..d70da09b4ab8
--- /dev/null
+++ b/libcxx/include/__iterator/iter_swap.h
@@ -0,0 +1,107 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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___ITERATOR_ITER_SWAP_H
+#define _LIBCPP___ITERATOR_ITER_SWAP_H
+
+#include <__config>
+#include <__iterator/concepts.h>
+#include <__iterator/iter_move.h>
+#include <__iterator/iterator_traits.h>
+#include <__iterator/readable_traits.h>
+#include <__ranges/access.h>
+#include <concepts>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+
+namespace ranges {
+namespace __iter_swap {
+  template<class _I1, class _I2>
+  void iter_swap(_I1, _I2) = delete;
+
+  template<class _T1, class _T2>
+  concept __unqualified_iter_swap = requires(_T1&& __x, _T2&& __y) {
+    iter_swap(_VSTD::forward<_T1>(__x), _VSTD::forward<_T2>(__y));
+  };
+
+  template<class _T1, class _T2>
+  concept __readable_swappable =
+    indirectly_readable<_T1> && indirectly_readable<_T2> &&
+    swappable_with<iter_reference_t<_T1>, iter_reference_t<_T2>>;
+
+  struct __fn {
+    template <class _T1, class _T2>
+      requires __unqualified_iter_swap<_T1, _T2>
+    _LIBCPP_HIDE_FROM_ABI
+    constexpr void operator()(_T1&& __x, _T2&& __y) const
+      noexcept(noexcept(iter_swap(_VSTD::forward<_T1>(__x), _VSTD::forward<_T2>(__y))))
+    {
+      (void)iter_swap(_VSTD::forward<_T1>(__x), _VSTD::forward<_T2>(__y));
+    }
+
+    template <class _T1, class _T2>
+      requires (!__unqualified_iter_swap<_T1, _T2>) &&
+               __readable_swappable<_T1, _T2>
+    _LIBCPP_HIDE_FROM_ABI
+    constexpr void operator()(_T1&& __x, _T2&& __y) const
+      noexcept(noexcept(ranges::swap(*_VSTD::forward<_T1>(__x), *_VSTD::forward<_T2>(__y))))
+    {
+      ranges::swap(*_VSTD::forward<_T1>(__x), *_VSTD::forward<_T2>(__y));
+    }
+
+    template <class _T1, class _T2>
+      requires (!__unqualified_iter_swap<_T1, _T2> &&
+                !__readable_swappable<_T1, _T2>) &&
+               indirectly_movable_storable<_T1, _T2> &&
+               indirectly_movable_storable<_T2, _T1>
+    _LIBCPP_HIDE_FROM_ABI
+    constexpr void operator()(_T1&& __x, _T2&& __y) const
+      noexcept(noexcept(iter_value_t<_T2>(ranges::iter_move(__y))) &&
+               noexcept(*__y = ranges::iter_move(__x)) &&
+               noexcept(*_VSTD::forward<_T1>(__x) = declval<iter_value_t<_T2>>()))
+    {
+      iter_value_t<_T2> __old(ranges::iter_move(__y));
+      *__y = ranges::iter_move(__x);
+      *_VSTD::forward<_T1>(__x) = _VSTD::move(__old);
+    }
+  };
+} // end namespace __iter_swap
+
+inline namespace __cpo {
+  inline constexpr auto iter_swap = __iter_swap::__fn{};
+} // namespace __cpo
+
+} // namespace ranges
+
+template<class _I1, class _I2 = _I1>
+concept indirectly_swappable =
+  indirectly_readable<_I1> && indirectly_readable<_I2> &&
+  requires(const _I1 __i1, const _I2 __i2) {
+    ranges::iter_swap(__i1, __i1);
+    ranges::iter_swap(__i2, __i2);
+    ranges::iter_swap(__i1, __i2);
+    ranges::iter_swap(__i2, __i1);
+  };
+
+#endif // !defined(_LIBCPP_HAS_NO_RANGES)
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___ITERATOR_ITER_SWAP_H