static <A, B> TreeMap<A, B> asTreeMap(Map<A, B> map, Comparator<A> comparator default null) {
  if (map cast TreeMap && eq(map.comparator(), comparator))
    ret map;
  var m2 = new TreeMap(comparator);
  m2.putAll(map);
  ret m2;
}

static <A, B> TreeMap<A, B> asTreeMap(Comparator<A> comparator, Map<A, B> map) {
  ret asTreeMap(map, comparator);
}