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

[Ambrose Leeb via cfe-commits]

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@@ -1207,6 +1207,12 @@ def IsWithinLifetime : LangBuiltin<"CXX_LANG"> {
   let Prototype = "bool(void*)";
 }
 
+def MetaIsType : LangBuiltin<"CXX_LANG"> {
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Sirraide wrote:

I wonder if we should move these into a separate file, because we’ll be adding like, what, 50–100 of them? Maybe a `MetaBuiltins.td` is in order

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