tests/compiler/dart2js/cps_ir/input/constructor_3.dart

class Base0 {
  Base0() {
    print('Base0');
  }
}
class Base extends Base0 {
  var x;
  Base(this.x);
}
class Sub extends Base {
  var y;
  Sub(x, this.y) : super(x) {
    print(x);
  }
}
main() {
  print(new Sub(1, 2).x);
}