here f2 will be null

class Field1 {
  Field1() {
    print("Field1()");
  }
}

class Field2 {
  Field2() {
    print("Field2()");
  }
}

class Field3 {
  Field1 f = new Field1();
  Field2 f2 = new Field2();
  Field3({this.f2}) {
    print(this.f2);
    print("Field3()");
  }
}



void main() {
  Field3 f3 = new Field3();
}