Swift 3 - iterate over generic collection - swift3

Question

I have struct Queue<T> that is based on a LinkedList<T>() I want to be able to iterate over the element in the queue and do something with them.
After doing some digging, I believe I have to inherit from Sequence and do something like this:
extension Sequence {
public func makeIterator() -> CountableRange<T>.Iterator {
return (0..<self).makeIterator()
}
}
and after I can have a function in my Queue class something like:
func iter(q: T) -> T? {
for i in q {
}
}
except the extension throws Use of undeclared type 'T' and the for loop a Type 'T' does not conform to protocol 'Sequence'
I am fairly new to Swift and I understand what I have to do I just don't know how to do it and find most explanations quite confusing. Could someone point me in the right direction?
import Foundation
public struct Queue<T> : Sequence{
fileprivate var list = LinkedList<T>()
public var queueCount : Int {
return list.getCount()
}
public var isEmpty: Bool {
return list.isEmpty
}
public mutating func enqueue(_ element: T) {
list.append(value: element)
}
public mutating func dequeue() -> T? {
guard !list.isEmpty, let element = list.first else { return nil }
list.remove(node: element)
return element.value
}
public func peek() -> T? {
return list.first?.value
}
func iter(q: T) -> T? {
for i in q {
}
}
}
extension Queue: CustomStringConvertible {
// 2
public var description: String {
// 3
return list.description
}
}
extension Sequence {
public func makeIterator() -> CountableRange<T>.Iterator {
return (0..<self).makeIterator()
}
}