Upgrade to 2022-era LLVM LIBCXX

third_party/libcxx/__utility/forward_like.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___UTILITY_FORWARD_LIKE_H
+#define _LIBCPP___UTILITY_FORWARD_LIKE_H
+
+#include <__config>
+#include <__type_traits/conditional.h>
+#include <__type_traits/is_const.h>
+#include <__type_traits/is_reference.h>
+#include <__type_traits/remove_reference.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 23
+
+template <class _Ap, class _Bp>
+using _CopyConst = _If<is_const_v<_Ap>, const _Bp, _Bp>;
+
+template <class _Ap, class _Bp>
+using _OverrideRef = _If<is_rvalue_reference_v<_Ap>, remove_reference_t<_Bp>&&, _Bp&>;
+
+template <class _Ap, class _Bp>
+using _ForwardLike = _OverrideRef<_Ap&&, _CopyConst<remove_reference_t<_Ap>, remove_reference_t<_Bp>>>;
+
+template <class _Tp, class _Up>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto forward_like(_LIBCPP_LIFETIMEBOUND _Up&& __ux) noexcept
+    -> _ForwardLike<_Tp, _Up> {
+  return static_cast<_ForwardLike<_Tp, _Up>>(__ux);
+}
+
+#endif // _LIBCPP_STD_VER >= 23
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___UTILITY_FORWARD_LIKE_H