@ParametricNullness
    public V rightValue() {
      return right;
    }

    @Override
    public boolean equals(@Nullable Object object) {
      if (object instanceof ValueDifference) {
        ValueDifference<?> that = (ValueDifference<?>) object;
        return Objects.equals(this.left, that.leftValue())
            && Objects.equals(this.right, that.rightValue());
      }
      return false;
    }

    @ParametricNullness
    public V rightValue() {
      return right;
    }

    @Override
    public boolean equals(@Nullable Object object) {
      if (object instanceof ValueDifference) {
        ValueDifference<?> that = (ValueDifference<?>) object;
        return Objects.equals(this.left, that.leftValue())
            && Objects.equals(this.right, that.rightValue());
      }
      return false;
    }