Upgrade to 2022-era LLVM LIBCXX

third_party/libcxx/__ranges/enable_view.h

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+// -*- 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___RANGES_ENABLE_VIEW_H
+#define _LIBCPP___RANGES_ENABLE_VIEW_H
+
+#include <__concepts/derived_from.h>
+#include <__concepts/same_as.h>
+#include <__config>
+#include <__type_traits/is_class.h>
+#include <__type_traits/is_convertible.h>
+#include <__type_traits/remove_cv.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+namespace ranges {
+
+struct view_base { };
+
+template<class _Derived>
+  requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
+class view_interface;
+
+template<class _Op, class _Yp>
+  requires is_convertible_v<_Op*, view_interface<_Yp>*>
+void __is_derived_from_view_interface(const _Op*, const view_interface<_Yp>*);
+
+template <class _Tp>
+inline constexpr bool enable_view = derived_from<_Tp, view_base> ||
+  requires { ranges::__is_derived_from_view_interface((_Tp*)nullptr, (_Tp*)nullptr); };
+
+} // namespace ranges
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___RANGES_ENABLE_VIEW_H