.isSubtypeOf(superclass));
  }

  public void testGetSubtypeOf_impossibleWildcard() {
    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

  }

  private interface NumberList<T extends Number> {}

  public void testImplicitUpperBoundForWildcards() {
    assertAssignable(
        new TypeToken<NumberList<? extends Number>>() {}, new TypeToken<NumberList<?>>() {});
    assertAssignable(
        new TypeToken<NumberList<? super Integer>>() {}, new TypeToken<NumberList<?>>() {});
  }

  }

  private interface NumberList<T extends Number> {}

  public void testImplicitUpperBoundForWildcards() {
    assertAssignable(
        new TypeToken<NumberList<? extends Number>>() {}, new TypeToken<NumberList<?>>() {});
    assertAssignable(
        new TypeToken<NumberList<? super Integer>>() {}, new TypeToken<NumberList<?>>() {});
  }