TypeToken<List<? extends Number>> numberList = new TypeToken<List<? extends Number>>() {};
    abstract class StringList implements List<String> {}
    assertThrows(IllegalArgumentException.class, () -> numberList.getSubtype(StringList.class));
  }

  private static class OwnerTypeSubtypingTests extends SubtypeTester {
    @TestSubtype
    public Mall<Outdoor>.Shop<Electronics> innerTypeIsSubtype(