Enum + Option -> Modern OptionSet

Enum+Option.swift

// Playground

protocol Option: RawRepresentable, Hashable, CaseIterable {}

extension Set where Element: Option {
    var rawValue: Int {
        var rawValue = 0
        for (index, element) in Element.allCases.enumerated() where contains(element) {
            rawValue |= (1 << index)
        }
        return rawValue
    }
}

// MARK: - Example

enum Topping: String, Option {
    case pepperoni, onions, bacon, extraCheese, greenPeppers, pineapple
}
typealias Toppings = Set<Topping>

struct Pizza {
    let toppings: Toppings
}

let pizza = Pizza(toppings: [.bacon, .onions, .pepperoni])
print("Pizza:", pizza)