class Sub extends Super {
  Sub.arg0()
      : super.arg0(),
        field = 42;
  Sub.arg1(a)
      : super.arg1(a),
        field = 42;
  Sub.arg2(a, b)
      : super.arg2(a, b),
        field = 42;
  var field;
}

class Super {
  Super.arg0();
  Super.arg1(a);
  Super.arg2(a, b);
}