name resolution for guard patterns

[dianne]

This PR provides an initial implementation of name resolution for guard patterns (RFC 3637). This does not change the requirement that the bindings on either side of an or-pattern must be the same (proposal here); the code that handles that is separate from what this PR touches, so I'm saving it for a follow-up.

On a technical level, this separates "collecting the bindings in a pattern" (which was already done for or-patterns) from "introducing those bindings into scope". I believe the approach used here can be extended straightforwardly in the future to work with if let guard patterns, but I haven't tried it myself since we don't allow those yet.

Tracking issue for guard patterns: #129967

cc @Nadrieril

[rustbot]

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[Nadrieril]

@bors try @rust-timer queue

[bors]

⌛ Trying commit d7ac436 with merge f04862f...

[bors]

☀️ Try build successful - checks-actions
Build commit: f04862f (f04862fbe36c5246e1b11151b86d39c1ae766cb5)

[rust-timer]

Finished benchmarking commit (f04862f): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	1.0%	[1.0%, 1.0%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.0%	[1.0%, 1.0%]	1

Max RSS (memory usage)

Results (primary 0.5%, secondary -1.3%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.7%	[0.5%, 1.4%]	20
Regressions ❌ (secondary)	1.6%	[1.6%, 1.6%]	1
Improvements ✅ (primary)	-1.3%	[-1.8%, -0.9%]	2
Improvements ✅ (secondary)	-2.8%	[-3.4%, -2.2%]	2
All ❌✅ (primary)	0.5%	[-1.8%, 1.4%]	22

Cycles

Results (primary -0.6%, secondary -1.8%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.6%	[-1.0%, -0.4%]	30
Improvements ✅ (secondary)	-1.8%	[-1.8%, -1.8%]	1
All ❌✅ (primary)	-0.6%	[-1.0%, -0.4%]	30

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 769.201s -> 769.203s (0.00%)
Artifact size: 365.25 MiB -> 365.08 MiB (-0.05%)

[dianne]

I might know how to get perf back to where it was before and trim down this PR's diff. I'll try pushing an update later. @rustbot author

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[dianne]

Actually, I don't think I'm going to try improving the perf yet. I have no idea what's causing the instruction count regression in nalgebra. That's the only instruction count regression, and I don't see how this change could have caused it. late_resolve_crate is only 1.46% of the total execution already, so getting 1% more instructions from this change would be pretty wild, especially considering the time delta in the perf report for late_resolve_crate is a -1.28% improvement. If there's something going on here that needs fixing, I might need help figuring out what it is.

I did notice I was missing an important test though, so I've added that. (diff) @rustbot ready