.isEqualTo(returnType);
    }
    return sub;
  }

  /**
   * Call this in a {@link TestSubtype} public method asserting that subtype relationship does not
   * hold.
   */
  final <X> @Nullable X notSubtype(@SuppressWarnings("unused") Object sub) {
    Type returnType = method.getGenericReturnType();
    Type paramType = getOnlyParameterType();

          .isEqualTo(returnType);
    }
    return sub;
  }

  /**
   * Call this in a {@link TestSubtype} public method asserting that subtype relationship does not
   * hold.
   */
  final <X> @Nullable X notSubtype(@SuppressWarnings("unused") Object sub) {
    Type returnType = method.getGenericReturnType();
    Type paramType = getOnlyParameterType();