public boolean isSubtypes(List<Type> ts, List<Type> ss) {
        while (ts.tail != null && ss.tail != null
               /*inlined: ts.nonEmpty() && ss.nonEmpty()*/ &&
               isSubtype(ts.head, ss.head)) {
            ts = ts.tail;
            ss = ss.tail;
        }
        return ts.tail == null && ss.tail == null;
        /*inlined: ts.isEmpty() && ss.isEmpty();*/
    }