[clang] [clang][Sema] Early exit when default arg contains errors (PR #175582)

[Shafik Yaghmour via cfe-commits]

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@@ -3190,6 +3190,11 @@ bool Sema::SubstDefaultArgument(
            << FD << PatternExpr->getSourceRange();
   }
 
+  // Exit early if argument has error, we should've emitted the diagnostic when
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shafik wrote:

Yeah, it is not clear to me this is a great solution, what is the diagnostic emitted look like? Have you looked into catching this at an earlier point?

https://github.com/llvm/llvm-project/pull/175582