static <A extends IHasChangeListeners, B> SimpleLiveValue<B>
  liveValue_hasChangeListeners(A object, Class<B> type default null,
    IF0<B> getter, IVF1<B> setter default null) {
  SimpleLiveValue<B> value = new(type, getter!);
  addWeakChangeListener(object, value, val -> val.set(getter!));
  value.onChange(-> { setter?.get(value!); });
  ret value;
}

Began life as a copy of #1031140