tailrec.scala:6: error: could not optimize @tailrec annotated method
  def facfail(n: Int): Int =
      ^
tailrec.scala:42: error: could not optimize @tailrec annotated method
  @tailrec def fail1(x: Int): Int = fail1(x)
               ^
tailrec.scala:45: error: could not optimize @tailrec annotated method
  @tailrec def fail2[T](xs: List[T]): List[T] = xs match {
               ^
three errors found