[clang] [clang-tools-extra] [Clang] Add a builtin that deduplicate types into a pack (PR #106730)

[Younan Zhang via cfe-commits]

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@@ -228,7 +228,9 @@ void threadSafetyCleanup(BeforeSet *Cache);
 
 // FIXME: No way to easily map from TemplateTypeParmTypes to
 // TemplateTypeParmDecls, so we have this horrible PointerUnion.
-typedef std::pair<llvm::PointerUnion<const TemplateTypeParmType *, NamedDecl *>,
+typedef std::pair<llvm::PointerUnion<const TemplateTypeParmType *, NamedDecl *,
+                                     const TemplateSpecializationType *,
+                                     const SubstBuiltinTemplatePackType *>,
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zyn0217 wrote:

I think we could leave it as-is :) No fixme nor issue is required because one would notice that when adding new types

https://github.com/llvm/llvm-project/pull/106730