scala3-DependentMethodFuncTypes2.scala

scala> case class IntLinkedList(head: Int, tail: Option[IntLinkedList]) extends LinkedList:
     |   type Item = Int
// defined case class IntLinkedList

scala> val ill = IntLinkedList(0,
     |   Some(IntLinkedList(1, Some(IntLinkedList(2, None)))))
val ill: IntLinkedList = IntLinkedList(0,Some(IntLinkedList(1,Some(IntLinkedList(2,None)))))

scala> head(ill)
     | tail(ill)
     | head(tail(ill).get)
     | head(tail(tail(ill).get).get)
val res0: ill.Item = 0
val res1: Option[LinkedList] = Some(IntLinkedList(1,Some(IntLinkedList(2,None))))
val res2: LinkedList#Item = 1
val res3: LinkedList#Item = 2
     
scala> h(ill)
     | t(ill)
     | h(t(ill).get)
     | h(t(t(ill).get).get)
val res4: ill.Item = 0
val res5: Option[LinkedList] = Some(IntLinkedList(1,Some(IntLinkedList(2,None))))
val res6: LinkedList#Item = 1
val res7: LinkedList#Item = 2