abstract class Bomb {
	type T
	val x: T

	def size(that: T): Int
}

class StringBomb extends Bomb {
	type T = String
	val x = "abc"
	def size(that: String): Int = that.length
}

class IntBomb extends Bomb { 
	type T = Int
	val x = 10

	def size(that: Int) = x + that
}

case class Mean(var bomb: Bomb)

object Main extends App {
	def foo(x: Mean) = x match {
		case Mean(b) => 
			// b is assumed to be a stable identifier, but it can actually be mutated
			println(b.size({ mutate(); b.x }))
	}

	def mutate() {
	   	m.bomb = new IntBomb
	}

	val m = Mean(new StringBomb)
	foo(m)
}