static Set<Class> allInterfacesImplementedBy(O o) {
  ret allInterfacesImplementedBy(_getClass(o));
}

static Set<Class> allInterfacesImplementedBy(Class c) {
  if (c == null) null;
  new HashSet<Class> set;
  allInterfacesImplementedBy_find(c, set);
  ret set;
}

svoid allInterfacesImplementedBy_find(Class c, Set<Class> set) {
  if (c.isInterface() && !set.add(c)) ret;
  do {
    for (Class intf : c.getInterfaces())
      allInterfacesImplementedBy_find(intf, set);
  } while ((c = c.getSuperclass()) != null);
}