[Clang] Handle ?: operator in fold expression

Author: azmat-y

clang/lib/Sema/SemaExpr.cpp

@@ -8966,6 +8966,9 @@ ExprResult Sema::ActOnConditionalOp(SourceLocation QuestionLoc,
       commonExpr = MatExpr.get();
     }
 
+    if (commonExpr->getDependence() & ExprDependence::UnexpandedPack)
+      return ExprError();
+
     opaqueValue = new (Context) OpaqueValueExpr(commonExpr->getExprLoc(),
                                                 commonExpr->getType(),
                                                 commonExpr->getValueKind(),

clang/lib/Sema/SemaTemplateVariadic.cpp

@@ -1510,7 +1510,7 @@ static void CheckFoldOperand(Sema &S, Expr *E) {
   E = E->IgnoreImpCasts();
   auto *OCE = dyn_cast<CXXOperatorCallExpr>(E);
   if ((OCE && OCE->isInfixBinaryOp()) || isa<BinaryOperator>(E) ||
-      isa<AbstractConditionalOperator>(E)) {
+      isa<AbstractConditionalOperator>(E) || isa<RecoveryExpr>(E)) {
     S.Diag(E->getExprLoc(), diag::err_fold_expression_bad_operand)
         << E->getSourceRange()
         << FixItHint::CreateInsertion(E->getBeginLoc(), "(")