[clang] [lldb] [Clang] Improve Sema diagnostic performance for __builtin_counted_by_ref (PR #116719)

[Aaron Ballman via cfe-commits]

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@@ -14690,6 +14690,13 @@ void Sema::FinalizeDeclaration(Decl *ThisDecl) {
     }
   }
 
+  // The result of __builtin_counted_by_ref cannot be assigned to a variable.
+  // It allows leaking and modification of bounds safety information.
+  if (IsBuiltinCountedByRef(VD->getInit()))
+    Diag(VD->getInit()->getExprLoc(),
+         diag::err_builtin_counted_by_ref_cannot_leak_reference)
+        << VD->getInit()->getSourceRange();
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AaronBallman wrote:

Should we split this off into a helper function like `bool CheckInvalidBuiltinCountedByRef(const Expr *E);` ?

https://github.com/llvm/llvm-project/pull/116719