static Map<Class, Set<S>> allFields_cache = weakHashMap();

static Set<S> allFields(O o) {
  Class _c = _getClass(o);
  Set<S> fields = allFields_cache.get(_c);
  if (fields == null)
    allFields_cache.put(_c, fields = asTreeSet(keys(getOpt_getFieldMap(_c))));
  return fields;
}