[clang] [clang][Sema] support block pointers as non-type template parameters (PR #191694)

[Oliver Hunt via cfe-commits]

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@@ -6844,7 +6849,7 @@ void CXXNameMangler::mangleValueInTemplateArg(QualType T, const APValue &V,
           Out << "cv";
           mangleType(T);
         }
-        if (T->isPointerType())
+        if (T->isPointerType() || T->isBlockPointerType())
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ojhunt wrote:

I'd rather avoid the constant isPointer || isBlockPointer -- there's `hasPointerRepresentation` but it seems plausible that that is too generic and will match incorrect types. A helper `isNTTPCompatiblePointerType()`seems like it might be acceptable - @mizvekov do you have thoughts here? (it could even take an ASTContext so that the answer would be target gated if we really wanted?)

https://github.com/llvm/llvm-project/pull/191694