class BaseWithTypeVar<T> {}
    class Outer<O> {
      class Sub<X> extends BaseWithTypeVar<List<X>> {}

      class Sub2<Y extends Sub2<Y>> extends BaseWithTypeVar<List<Y>> {}
    }
    ParameterizedType subtype =
        (ParameterizedType)
            new TypeToken<BaseWithTypeVar<List<?>>>() {}.getSubtype(Outer.Sub.class).getType();