EnumEnumerable for Swift3.0

EnumEnumerable.swift

public protocol EnumEnumerable {
    associatedtype Case = Self
}

public extension EnumEnumerable where Case: Hashable {
    private static var iterator: AnyIterator<Case> {
        var n = 0
        return AnyIterator {
            defer { n += 1 }
            let next = withUnsafePointer(&n) { UnsafePointer<Case>($0).pointee }
            return next.hashValue == n ? next : nil
        }
    }

    public static func enumerate() -> EnumeratedSequence<AnySequence<Case>> {
        return AnySequence(self.iterator).enumerated()
    }

    public static var cases: [Case] {
        return Array(self.iterator)
    }

    public static var count: Int {
        return self.cases.count
    }
}