int set setter1(_) {}
dynamic set setter2(_) {}
void set setter3(_) {}
set setter4(_) {}

class Class1 {
  int set setter1(_) {}
  int operator []=(a, b) {}
}

class Class2 {
  dynamic set setter2(_) {}
  dynamic operator []=(a, b) {}
}

class Class3 {
  void set setter3(_) {}
  void operator []=(a, b) {}
}

class Class4 {
  set setter4(_) {}
  operator []=(a, b) {}
}

main() {}