[clang] [BoundsSafety][Clang][Sema][AST] Introduce CThisExpr for C __counted_by attributes (PR #199241)

[Marco Elver via cfe-commits]

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@@ -1510,6 +1510,41 @@ class DeclRefExpr final
   }
 };
 
+class CThisExpr : public Expr {
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melver wrote:

Why no comments?

https://github.com/llvm/llvm-project/pull/199241