enum StarRating:Int,Comparable {
    case unknown = 0
    case star1
    case star2
    case star3
    case star4
    case star5
    
    static func < (lhs: StarRating, rhs: StarRating)->Bool {
        return lhs.rawValue < rhs.rawValue
    }
}

struct StarRatingSet:OptionSet {
    typealias RawValue = Int
    typealias Element = StarRatingSet //<-- This is the line I had to add
    var rawValue: Int
    
    static let unknown = StarRatingSet(rawValue: 1 << 0)
    static let star1 = StarRatingSet(rawValue: 1 << 1)
    static let star2 = StarRatingSet(rawValue: 1 << 2)
    static let star3 = StarRatingSet(rawValue: 1 << 3)
    static let star4 = StarRatingSet(rawValue: 1 << 4)
    static let star5 = StarRatingSet(rawValue: 1 << 5)
    
    static let star4Plus:StarRatingSet = [.star4,.star5]
    static let star3Plus:StarRatingSet = [.star3,.star4,.star5]
    static let star2Plus:StarRatingSet = [.star2,.star3,.star4,.star5]
    static let star1Plus:StarRatingSet = [.star1,.star2,.star3,.star4,.star5]
    static let any:StarRatingSet = [.unknown,.star1,.star2,.star3,.star4,.star5]
    
    func contains(_ rating:StarRating) -> Bool { //<- This might be the issue
        return self.contains(StarRatingSet(rating))
    }
    
    var highest:StarRating {
        if self.contains(.star5) {return .star5}
        else if self.contains(.star4) {return .star4}
        else if self.contains(.star3) {return .star3}
        else if self.contains(.star2) {return .star2}
        else if self.contains(.star1) {return .star1}
        return .unknown
    }
    
    var lowest:StarRating {
        if self.contains(.star1) {return .star1}
        else if self.contains(.star2) {return .star2}
        else if self.contains(.star3) {return .star3}
        else if self.contains(.star4) {return .star4}
        else if self.contains(.star5) {return .star5}
        return .unknown
    }
}