MyList.scala

sealed trait MyList[+T]

case object MyNil extends MyList[Nothing]
case class MyCons[+T](head: T, tail: MyList[T]) extends MyList[T]

object MyList { 
  object :: { 
    def unapply[T](list: MyList[T]): Option[(T, MyList[T])] = list match { 
      case MyCons(x, xs) => Some((x, xs))
      case MyNil => None
    }
  }
  def apply[T](x: T, xs: MyList[T]): MyList[T] = MyCons(x, xs) 
}

import MyList._

val list = MyList(1, MyList(2, MyList(3, MyNil)))
val a :: b :: c :: xs = list

// Output:
// a: Int = 1
// b: Int = 2
// c: Int = 3
// xs: MyList[Int] = MyNil