// returns true if change
sbool cSmartSetField_withConverter(Concept c, S field, O value, ValueConverterForField converter) ctex {
  Field f = setOpt_findField(c.getClass(), field);
  
  if (f != null && converter != null && value != null) {
    OrError<O> result = converter.convertValue(c, f, value);
    if (result == null) fail("Unknown conversion " + className(value) + " => " + f);
    if (!result.ok()) fail("Unknown conversion " + className(value) + " => " + f + ": " + result.error());
    ret _csetField(c, field, result!);
  }
 
  ret _csetField(c, field, value);
}