* type variable too.
   */
  final @Nullable TypeToken<? super T> getGenericSuperclass() {
    if (runtimeType instanceof TypeVariable) {
      // First bound is always the super class, if one exists.
      return boundAsSuperclass(((TypeVariable<?>) runtimeType).getBounds()[0]);
    }
    if (runtimeType instanceof WildcardType) {
      // wildcard has one and only one upper bound.

    TypeToken<?> parameterType = parameters.get(0).getType();
    Type[] typeArgs = ((ParameterizedType) parameterType.getType()).getActualTypeArguments();
    assertThat(typeArgs).hasLength(1);
    TypeVariable<?> captured = (TypeVariable<?>) typeArgs[0];
    assertThat(captured.getBounds()).asList().containsExactly(Object.class);
    assertThat(new TypeToken<List<?>>() {}.isSupertypeOf(parameterType)).isTrue();
  }

    TypeToken<?> parameterType = parameters.get(0).getType();
    Type[] typeArgs = ((ParameterizedType) parameterType.getType()).getActualTypeArguments();
    assertThat(typeArgs).hasLength(1);
    TypeVariable<?> captured = (TypeVariable<?>) typeArgs[0];
    assertThat(captured.getBounds()).asList().containsExactly(Object.class);
    assertThat(new TypeToken<List<?>>() {}.isSupertypeOf(parameterType)).isTrue();
  }