Upgrade to 2022-era LLVM LIBCXX

third_party/libcxx/__algorithm/ranges_reverse.h

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+//===----------------------------------------------------------------------===//
+//
+// 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___ALGORITHM_RANGES_REVERSE_H
+#define _LIBCPP___ALGORITHM_RANGES_REVERSE_H
+
+#include <__config>
+#include <__iterator/concepts.h>
+#include <__iterator/iter_swap.h>
+#include <__iterator/next.h>
+#include <__iterator/permutable.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__ranges/dangling.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 20
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace ranges {
+namespace __reverse {
+struct __fn {
+
+  template <bidirectional_iterator _Iter, sentinel_for<_Iter> _Sent>
+    requires permutable<_Iter>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  _Iter operator()(_Iter __first, _Sent __last) const {
+    if constexpr (random_access_iterator<_Iter>) {
+      if (__first == __last)
+        return __first;
+
+      auto __end = ranges::next(__first, __last);
+      auto __ret = __end;
+
+      while (__first < --__end) {
+        ranges::iter_swap(__first, __end);
+        ++__first;
+      }
+      return __ret;
+    } else {
+      auto __end = ranges::next(__first, __last);
+      auto __ret = __end;
+
+      while (__first != __end) {
+        if (__first == --__end)
+          break;
+
+        ranges::iter_swap(__first, __end);
+        ++__first;
+      }
+      return __ret;
+    }
+  }
+
+  template <bidirectional_range _Range>
+    requires permutable<iterator_t<_Range>>
+  _LIBCPP_HIDE_FROM_ABI constexpr
+  borrowed_iterator_t<_Range> operator()(_Range&& __range) const {
+    return (*this)(ranges::begin(__range), ranges::end(__range));
+  }
+
+};
+} // namespace __reverse
+
+inline namespace __cpo {
+  inline constexpr auto reverse = __reverse::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER >= 20
+
+#endif // _LIBCPP___ALGORITHM_RANGES_REVERSE_H