AnyPokemon Swift3

import Foundation

class Thunder { }
class Fire { }

protocol Pokemon {
    associatedtype PokemonType
    func attack(move:PokemonType)
}

struct Pikachu: Pokemon {
    typealias PokemonType = Thunder
    func attack(move: Thunder) { /*⚡️*/ }
}

class Charmander: Pokemon {
    func attack(move: Fire) { /*🔥*/ }
}

class Raichu: Pokemon {
    typealias PokemonType = Thunder
    func attack(move: Thunder) { /*⚡️*/ }
}

class AnyPokemon <V>: Pokemon {

    typealias PokemonType = V

    private let _attack: ((PokemonType) -> Void)

    required init<U:Pokemon>(_ pokemon: U) where U.PokemonType == PokemonType {
        _attack = pokemon.attack
    }

    func attack(move type:PokemonType) {
        return _attack(type)
    }
}

let thunderAttack = Thunder()
let fireAttack = Fire()

let pikachu: AnyPokemon<Thunder>
pikachu = AnyPokemon(Pikachu())
pikachu.attack(move: thunderAttack)

let raichu: AnyPokemon<Thunder>
raichu = AnyPokemon(Raichu())
raichu.attack(move: thunderAttack)

let electricPokemon = [pikachu, raichu]
for pokemon in electricPokemon {
    pokemon.attack(move: thunderAttack)
}

let charmander: AnyPokemon<Fire>
charmander = AnyPokemon(Charmander())
charmander.attack(move: fireAttack)