sealed-protected.scala

** Working */
  sealed class AB[+A] protected(protected val in: List[A], protected val out: List[A])
   object AB {
     class ABC(override protected val in: List[Int],
               override protected val out: List[Int])
       extends AB(in, out)
   }

  /**Not Working*/
  sealed class AB[+A] protected(protected val in: List[A], protected val out: List[A])
  class ABC(override protected val in: List[Int],
            override protected val out: List[Int])
    extends AB(in, out)

  /** Working */
  sealed class AB[+A](protected val in: List[A], protected val out: List[A])

  class ABC(override protected val in: List[Int],
            override protected val out: List[Int])
    extends AB(in, out)

/**Working*/
sealed trait AB[+A] {
    protected val in: List[A]
    protected val out: List[A]
  }

  class ABC(override protected val in: List[Int],
            override protected val out: List[Int])
    extends AB[Int]

    /** Not Working **/
    sealed class AB[+A] (protected val in: List[A], protected val out: List[A])
    class ABC(override protected val in: List[Int],
              override protected val out: List[Int])
      extends AB[Int]

/** Working **/
    sealed class AB[+A] (protected val in: List[A], protected val out: List[A])
    class ABC(override protected val in: List[Int],
              override protected val out: List[Int])
      extends AB[Int](in,out)