Upgrade to 2022-era LLVM LIBCXX

third_party/libcxx/__format/enable_insertable.h

@@ -0,0 +1,35 @@
+// -*- 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___FORMAT_ENABLE_INSERTABLE_H
+#define _LIBCPP___FORMAT_ENABLE_INSERTABLE_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+namespace __format {
+
+/// Opt-in to enable \ref __insertable for a \a _Container.
+template <class _Container>
+inline constexpr bool __enable_insertable = false;
+
+} // namespace __format
+
+#endif //_LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___FORMAT_ENABLE_INSERTABLE_H