Lapin

    def insert(key: T) = {
        @tailrec
        def recInsert(tree: SplayTree[T], k: (Node[T]) => Node[T]): Node[T] = {
            tree match {
                case Node(l, v, r) if key < v => recInsert(l, (tree) => k(Node(tree, v, r)))
                case Node(l, v, r) if key > v => recInsert(r, (tree) => k(Node(l, v, tree)))
                case tree: Node[T]            => k(tree)
                case tree: Leaf[T]            => k(tree.insert(key))
            }
        }
        recInsert(this, (tree) => tree).splay(key)
    }