帰納的可変長多相型（recursive variable-length polymorphic type）

gistfile1.txt

class Router<T...> {
    portions: [String];

    when (T) {
        case <>: {
        }
        otherwise: {
            leading: Router<* T.init>;
            parser: Parser<T.last>;
        }
    }
}

// 出力
class Router0 {
    portions: [String];
}

class Router1<T1> {
    leading: Router0;
    parser: Parser<T1>;

    portions: [String];
}

class Router2<T1, T2> {
    leading: Router1<T1>;
    parser: Parser<T2>;
    
    portions: [String];
}

...