[red-knot] type narrowing

[carljm]

Extend the UseDefMap to also track which constraints (provided by e.g. if tests) apply to each visible definition.

Uses a custom BitSet and BitSetArray to track which constraints apply to which definitions, while keeping data inline as much as possible.

[codspeed-hq]

CodSpeed Performance Report

Merging #12706 will degrade performances by 13.78%

_{Comparing cjm/narrow (15885c6) with main (a9847af)}

Summary

❌ 2 (👁 2) regressions
✅ 30 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	cjm/narrow	Change
👁	red_knot_check_file[cold]	51 ms	59.2 ms	-13.78%
👁	red_knot_check_file[incremental]	2.7 ms	3 ms	-9.39%

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

Formatter (stable)

✅ ecosystem check detected no format changes.

Formatter (preview)

✅ ecosystem check detected no format changes.

[MichaReiser]

This is great work and the documentation is excellent.

We may be able to remove quiet a bit of code from BitSet by using smallvec (if we want?) and we probably clone the narrowing constraints on every query run which we should avoid ;)

[carljm]

@MichaReiser Thanks for the excellent review! I think I've addressed all the comments. Lots of changes, so you may want to take another look.

[MichaReiser]

I only skimmed through. Thanks for addressing all the feedback and we're down to a 13% perf regression :)

[MichaReiser]

I do think we could make use of it but it would probably complicate the logic a bit because you need two versions of push and a into_iter version for constraints

For example, couldn't we avoid cloning the constraints and instead take them right from the symbol state?

[carljm]

Hmm, I made a reply comment about the "taking ownership in merge" thing but now I don't see it in the UI anywhere. Anyway the upshot was that you're right, I was able to do that; it didn't help the benchmarks but I left it in anyway. Going to go ahead and merge this, but if you see anything in those latest changes that looks dumb, don't hesitate to comment and I'll fix!