class Foo extends AnyRef with Application {
  var a = Predef.Array(1, 2, 4, 5);

  def swap(i: Int, j: Int): Unit = {
    val t = a(i); 
    a(i) = a(j); 
    a(j) = t // this will disappear!!!!
  }

  swap(2, 3);
}