Switch Resolver to operate on impl Write

[zbraniecki]

No description provided.

[zbraniecki]

Fixes #121

This is the second major change planned for 0.13. It introduces long awaited writer mode in which the main format_pattern takes any impl Write. I kept the old behavior as format_pattern_to_string -> Cow which allows for fast recovery of simple strings as &str.

The performance is really good, and I like the cleanups that it allowed me to do.

[zbraniecki]

Test	old	format_pattern	format_pattern_to_string
simple	7.9256 us	7.5823 us	7.3676 us
menubar	28.793 us	26.566 us	26.688 us
preferences	116.81 us	79.852 us	114.29 us
unescape	1.9559 us	1.0020 us	1.5760 us

Performance with just this patch is already improved even if to_string mode is used, and the impl Write is faster for anything except the simple benchmark.
I'm especially excited for the quite significant improvement on the "preferences" benchmark and I believe this can be further improved later on.

[zbraniecki]

I'm also removing the quirky DisplayableNode - #122

[zbraniecki]

@Manishearth can you skim through and confirm if the big picture looks good?

[zbraniecki]

Actually, one functional change happens to how we react to bomb attack.

Since we're populating a buffer, we can't just bail and return {lol9} identifier. Instead, we start populating with values and when we reach our limit, we just switch Scope::dirty to true and start bailing out. The output is visible in the reference test.

I believe it's a fair tradeoff and I'm comfortable with Rust producing different error-scenario output for when the number of placeables exceeds 100, since it's clearly outside of realm of what regular code should produce, but wanted to flag it explicitly here for any reviewers.

[Manishearth]

this seems good

[Pike]

Two comments:

Naming is hard, but I'd expect the signature of format_pattern to be similar across implementations. I'd give the new name to the writer one. Maybe just write_pattern?

Documentation for the new method is TBD still? I know we have problems with docs.rs, but still.

[Pike]

Forgot what I actually did: I mulled over cross-bundle refs and format-to-parts, and I don't think this change makes either scenario harder. Maybe format-to-parts would be easier, but then also DOM would be the one that doesn't want to consume strings. But all of that is hypothetical anyway.

From that big-picture POV, lgtm.

[zbraniecki]

Naming is hard, but I'd expect the signature of format_pattern to be similar across implementations. I'd give the new name to the writer one. Maybe just write_pattern?

I like it! Thank you! I'll update the names tomorrow.

Documentation for the new method is TBD still? I know we have problems with docs.rs, but still.

Yeah, I need to revisit docs before 0.13 release - they fell behind to the point where I want to do an overhaul rather than per-PR-updates before the release.