[clang] Fix crash on defaulted comparison recovery in Sema and AST (PR #210668)

[purnima shrivastava via cfe-commits]

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@@ -9042,7 +9042,7 @@ bool Sema::CheckExplicitlyDefaultedComparison(Scope *S, FunctionDecl *FD,
 
   // Perform any unqualified lookups we're going to need to default this
   // function.
-  if (S) {
+  if (S && !FD->isInvalidDecl()) {
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purnima-nlp wrote:

Correct 

https://github.com/llvm/llvm-project/pull/210668