Stack in Swift, implemented with a linked list

LinkedStack.swift

class Element<T> {
    let value: T
    var next: Element<T>? = nil
    
    init(value: T, next: Element<T>?)
    {
        self.value = value
        self.next = next
    }
}

struct LinkedStack<T>
{
    private var top: Element<T>?
    
    mutating func push(o: T) {
        let element = Element<T>(value: o, next: top)
        top = element
    }
    
    mutating func pop() -> T? {
        let result = top?.value
        top = top?.next
        return result
    }
}