Example of type erasure with Pokemon

TypeErasure.swift

class Thunder { }
class Fire { }

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

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

class Charmander: Pokemon {
    func attack(move: Fire) { print("🔥") }
}

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

// 付随型をジェネリクスに置き換えた抽象クラスを作る
// Swiftの言語仕様上、抽象クラスはないので、実際には「抽象クラスのようなもの」です
private class _AnyPokemonBase<PokemonType>: Pokemon {
    func attack(move:PokemonType) {
        // 空実装を提供する。オリジナルは abstruct() という関数を呼んでいる
        fatalError()
    }
}

// 抽象クラスを継承したラッパーを作る
private class _AnyPokemonBox<ConcretePokemon: Pokemon> : _AnyPokemonBase<ConcretePokemon.PokemonType> {
    let base :ConcretePokemon
    
    init(_ base :ConcretePokemon) {
        self.base = base
    }
    
    override func attack(move: ConcretePokemon.PokemonType) {
        self.base.attack(move)
    }
}

// AnyPokemonでは、_AnyPokemonBoxに処理を移譲する
final class AnyPokemon <PokemonType>: Pokemon {
    private let _box : _AnyPokemonBase<PokemonType>
    
    required init<U:Pokemon where U.PokemonType == PokemonType>(_ pokemon: U) {
        self._box = _AnyPokemonBox(pokemon)
    }
    
    func attack(move: PokemonType) {
        self._box.attack(move)
    }
}

let thunderAttack = Thunder()

let electricPokemon = [AnyPokemon(Pikachu()), AnyPokemon(Raichu())]
for pokemon in electricPokemon {
    pokemon.attack(thunderAttack)
}

without protocol oriented.

class Thunder { }

class AbstractPokemon<PokemonType> {
    func attack(move:PokemonType) {
        fatalError()
    }
}

class AbstractElectricPokemon : AbstractPokemon<Thunder> {
     override func attack(move: Thunder) { print("⚡️") }   
}

class Pikachu: AbstractElectricPokemon { }

class Raichu: AbstractElectricPokemon { }

let electricPokemon = [Pikachu(), Raichu()]
let thunderAttack = Thunder()

for pokemon in electricPokemon {
    pokemon.attack(thunderAttack)
}

// 英語は適当
I think...
Than deceive compiler by trick, provided abstract class can easy understood.

Each framework are making abstract class of their own.
Are you serious??