AbstractSequentialIterator is very rarely used, but we could still consider this helper, which might encourage more people to use it by permitting lambda expressions:

...becomes...

C last = last();
return AbstractSequentialIterator.of(
    first(),
    previous -> equalsOrThrow(previous, last) ? null : domain.next(previous));

But I guess I'm not really that excited about that particular example. And I'm not sure what the best method name would be.

This is similar to #2785, where I apparently excluded all Abstract* classes, and #2853.