@Override public boolean containsKey(Object o) {
switch (inc) {
case EQUAL: return m0.containsKey(o) && m1.containsKey(o);
case SUB0SUP1: return m0.containsKey(o);
case SUB1SUP0: return m1.containsKey(o);
}
throw new AssertionError();
}
@Override public boolean containsKey(Object o) {
if (!(o instanceof U2)) { return false; }
@SuppressWarnings("unchecked") U2<K0, K1> u = (U2<K0, K1>)o;
return u.type == 0? m0.containsKey(u.getT0()): m1.containsKey(u.getT1());
}