Introduces a Set type that stores enums, including those with associated types, and uniques on the label rather than the value.

LabelUniqueSet.swift

struct Label: Hashable {
    var label: String
}

protocol LabelUniquing {
    var label: Label { get }
}

extension LabelUniquing {
    var label: Label {
        let label = Mirror(reflecting: self).children.first?.label ?? String(describing: self)
        return Label(label: label)
    }
}

struct LabelUniqueSet<T: LabelUniquing> {
    private var valuesByLabel: [Label:T] = [:]
    mutating func insert(value: T) { valuesByLabel[value.label] = value }
    mutating func remove(label: Label) { valuesByLabel[label] = nil }
    func value(forLabel label: Label) -> T? { valuesByLabel[label] }
}


// Tests
enum Test: LabelUniquing {
    case a
    case b(value: String)
}

var set = LabelUniqueSet<Test>()
set.insert(value: .a)
set.insert(value: .b(value: "1"))
set.insert(value: .b(value: "2"))

let valueForB = set.value(forLabel: Label(label: "b"))!
print("This should be 2 ... \(valueForB)")

let valueForA = set.value(forLabel: Label(label: "a"))!
print("Value for a ... \(valueForA)")