Are objects passed as reference points if they are used as arguments in a function in Dart? If so, why doesn't this code work?

Question

enum Size{
  small,
  big,
}

class SizeWrap{
  Size size;
  
  SizeWrap(this.size);
  
}

void change(SizeWrap one, SizeWrap two){
  //one=two;
  one=SizeWrap(Size.