[clang] [BoundsSafety] Support late parsing for `counted_by` in type positions (PR #166491)

[Yeoul Na via cfe-commits]

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@@ -1238,6 +1238,13 @@ struct DeclaratorChunk {
 
   ParsedAttributesView AttrList;
 
+  /// Stores pointers to `Parser::LateParsedAttribute`. We use `void*` here
+  /// because `LateParsedAttribute` is a nested struct of `class Parser` and
+  /// cannot be forward-declared.
+  using LateAttrOpaquePtr = void *;
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rapidsna wrote:

I can do that. `LateParsedAttribute` already inherits from `LateParsedDeclaration`, so we could just hoist `LateParsedDeclaration` out of Parser and use it directly here. That seems cleaner than introducing yet another base class. Would you be open to that if it doesn't introduce too invasive changes?

https://github.com/llvm/llvm-project/pull/166491