Allow method calls in index expressions in hsIndexSimplify (#4240)

Author: vlstill

midend/hsIndexSimplify.cpp

@@ -20,6 +20,7 @@ void HSIndexFinder::addNewVariable() {
     if (locals != nullptr && (arrayIndex->right->is<IR::Operation_Ternary>() ||
                               arrayIndex->right->is<IR::Operation_Binary>() ||
                               arrayIndex->right->is<IR::Operation_Unary>() ||
+                              arrayIndex->right->is<IR::MethodCallExpression>() ||
                               arrayIndex->right->is<IR::PathExpression>())) {
         // Generate new local variable if needed.
         std::ostringstream ostr;