Replace fallible-iterator with tryiterator

[khuey]

As we've discussed over email. Just looking for feedback here, I have to release tryiterator on crates.io before we merge this.

[philipc]

These changes are all look trivial, which is good.

However, it appears that something like AttrsIter::count will silently discard any errors. Do you have any way to address that? This was the original reason we started using FallibleIterator.

Have you sort feedback from the larger Rust community about tryiterator?

[khuey]

These changes are all look trivial, which is good.

However, it appears that something like AttrsIter::count will silently discard any errors. Do you have any way to address that? This was the original reason we started using FallibleIterator.

It would be straightforward to add a TryIterator::count_ok.

Have you sort feedback from the larger Rust community about tryiterator?

I started to ask people for their opinions privately this week. I'm in no hurry to merge this.

[philipc]

It would be straightforward to add a TryIterator::count_ok.

Right, but it would need a lint to determine the cases where count was wrong.

[khuey]

Another option that was suggested to me is to add an intentionally conflicting TryIteratorExt::count so that iter.count() won't work without qualifying which trait is being used.