javac/comp/Check.java

1516             List<Type> ts1 = excl(t, ts.tail);
1517             if (types.isSubtype(ts.head, t)) return ts1;
1518             else if (ts1 == ts.tail) return ts;
1519             else return ts1.prepend(ts.head);
1525     List<Type> union(List<Type> ts1, List<Type> ts2) {
1526         List<Type> ts = ts1;
1534     List<Type> diff(List<Type> ts1, List<Type> ts2) {
1535         List<Type> ts = ts1;
1543     public List<Type> intersect(List<Type> ts1, List<Type> ts2) {
1545         for (List<Type> l = ts1; l.nonEmpty(); l = l.tail)
1548             if (subset(l.head, ts1)) ts = incl(l.head, ts);