A Swift protocol that is using an enum with a generic associated type

AssociatedProtocol.swift

import Foundation
import UIKit


//: # The problem: Protocol that is using an enum with generic associated type
enum GenericEnum<T> {
    case Unassociated
    case Associated(T)
}

protocol AssociatedProtocol: class {
    typealias Association
    func foo() -> GenericEnum<Association>
}

//: ## Short example of the issue
//: Protocol can only be used as a generic constraint because it has associated type requirements
let bar = [AssociatedProtocol<String>]()


//: ## Long example of the issue

// working examples
class StringProtocol: AssociatedProtocol {
        func foo() -> GenericEnum<String> {
            // todo...
            return .Associated("foo")
        }
}

class StringListProtocol: AssociatedProtocol {
        func foo() -> GenericEnum<[String]> {
            // todo...
            return .Associated(["foo"])
        }

}

let aStringListProtocol = StringListProtocol()
let returnedEnum = aStringListProtocol.foo()

switch returnedEnum {
case .Unassociated:
        println("Unassociated")
case .Associated(let strings):
        println("strings: \(strings)")
}

// not working
class StringProtocolList: AssociatedProtocol {
    typealias StringProtocolArray = [AssociatedProtocol]

    var stringProtocols: StringProtocolArray = []

    func foo() -> GenericEnum<StringProtocolArray> {
        let stringProtocol = StringProtocol()
        stringProtocols.append(stringProtocol)

        // todo...

        return .Associated(stringProtocols)
    }
}

let list = StringProtocolList()
let foos = list.foo()