[clang] [clang-tools-extra] [clang] Implement CWG2398 provisional TTP matching to class templates (PR #94981)

[Matheus Izvekov via cfe-commits]

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@@ -412,6 +445,30 @@ class SubstTemplateTemplateParmStorage
                       std::optional<unsigned> PackIndex);
 };
 
+class DeducedTemplateStorage : public UncommonTemplateNameStorage,
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mizvekov wrote:

This one is a too internal detail of how the different kinds of TemplateNames are implemented. Ie if we can't fit everything we need in one pointer, then we allocate separate storage for it.
Might be more useful to document the DeducedTemplate itself.

https://github.com/llvm/llvm-project/pull/94981