Factorial in scala with trampolines

Factorial.scala

sealed trait Bounce[A]
case class Done[A](result: A) extends Bounce[A]
case class Call[A](thunk: () => Bounce[A]) extends Bounce[A]

def trampoline[A](bounce: Bounce[A]): A = bounce match {
  case Call(thunk) => trampoline(thunk())
  case Done(x) => x
}

def factorial(n: Int, sum: BigInt): Bounce[BigInt] {
	if (n <= 2) Done(sum)
	else Call(() => Factorial(n - 1, n * sum))
}

object Factorial extends Application {
	println(trampoline(factorial(100000, 1)))
}