class A {
  method m(i: int) returns (x: int) 
    ensures x == i;
  {
    var j := 0;
    var v [v == i + j];
    x := v;
  }

  method n() {
    var x := 0;
    var y := 1;
    var z := 2;  
  }
}

class B refines A {
  transforms m(i: int) returns (x: int, y: int)  
    ensures y == 0;
  {
    var t := 0;
    _
    replaces v by {
      var v := i + j; 
      call t, j := m(0);
      y := j;
    }
    _
  }

  transforms n() {
    replaces * by {
      var x := 0;
      var y := x + 1;
      var z := 2*y;
    }
  }
}