You don't get it, you don't have to pepper the code. If you already have a `Circle` the check is unneeded. If you have done the check the type is constrained. Y

You don't get it, you don't have to pepper the code. If you already have a `Circle` the check is unneeded. If you have done the check the type is constrained. You do exactly as much or less checks as you would do pattern matches on sealed traits in Scala, except that it works as you except in all instances, not just with sealed traits.