code: public boolean isSubtypeUnchecked(Type t, List<Type> ts, Warner warn) {
          for (List<Type> l = ts; l.nonEmpty(); l = l.tail)
              if (!isSubtypeUnchecked(t, l.head, warn))
                  return false;
          return true;
      }
docs: Is t a subtype of every type in given list `ts'?<br>
  (not defined for Method and ForAll types)<br>
  Allows unchecked conversions.