[clang] [libcxx] [lldb] [clang]: implement std::meta::is_type (PR #211653)

[Nhat Nguyen via cfe-commits]

================
@@ -0,0 +1,38 @@
+// -*- 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_META
+#define _LIBCPP_META
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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changkhothuychung wrote:

we will move this header to the clang side eventually per [this comment](https://github.com/llvm/llvm-project/pull/211653#pullrequestreview-4775146573)

https://github.com/llvm/llvm-project/pull/211653