mash.swift

enum Enum {
    case foo(Int)
    case bar(String)
    case snog(Int)
}

let items: [Enum] = [.foo(1), .bar("hi"), .foo(2)]

let filtered = items.filter({ switch $0 { case .foo: return true; default: return false } })

let filtered2 = items.filter({ for case .foo in [$0] { return true }; return false })

extension Enum {
    var isFoo: Bool {
        switch self { case .foo: return true; default: return false }
    }
}

let filtered3 = items.filter({ $0.isFoo })

extension Enum {
    static func ~= (lhs: Enum, rhs: Enum) -> Bool {
        let lhsCase = Array(Mirror(reflecting: lhs).children)
        let rhsCase = Array(Mirror(reflecting: rhs).children)
        return lhsCase[0].0 == rhsCase[0].0
    }
}


let filtered4 = items.filter({ $0 ~= .foo(0) })
print(filtered4)

import Foundation

extension Enum {
    var caseName: String {
        return "\(Array(Mirror(reflecting: self).children)[0].0!)"
    }
    
    static func ~= <T>(lhs: Enum, rhs: (T) -> Enum) -> Bool {
        let lhsCase = lhs.caseName
        let prefixString = "Mirror for (\(T.self)) -> "
        let typeOffset = prefixString.characters.count
        let typeString = "\(Mirror(reflecting: rhs).description)"
        let rhsCase = typeString.substring(from: typeString.index(typeString.startIndex, offsetBy: typeOffset))
        return true
    }
}

let x = Enum.foo(_)
let rr = Mirror(reflecting: x).description
// print(Array(rr.children))

items[0] ~= x