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

[Aaron Ballman 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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AaronBallman wrote:

Could we introduce a base class, outside of `Parser`, that `LateParsedAttribute` could inherit from so we could use that type here?

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