Stack with Linked List implementation

StackWithLinkedList.swift

struct StackWithLinkedList<Element> {
    let stack = DoublyLinkedList<Element>()
    
    mutating func push(_ element: Element) {
        stack.append(element)
    }
    
    mutating func pop() -> DoublyLinkedListNode<Element>? {
        return stack.remove(node: stack.tail!)
    }
    
    func peek() -> DoublyLinkedListNode<Element>? {
        return stack.tail
    }
    
    var isEmpty: Bool {
        return stack.isEmpty
    }
    
    var count: Int {
        return stack.count
    }
}