Respect #[expect] the same way #[allow] is with the dead_code lint

[Urgau]

This PR makes the #[expect] attribute being respected in the same way the #[allow] attribute is with the dead_code lint.

The fix is much more involved than I would have liked (and it's not because I didn't tried!), because the implementation took advantage of the fact that firing a lint in a allow context is a no-op (for the user, as the lint is suppressed), to not fire-it at all.

And while it's fine for #[allow], it definitively isn't for #[expect], as the presence and absence of a lint is significant. So a big part of the PR is just adding the context information of whenever an item is on the worklist because of an [allow]/#[expect] or not.

Fixes #114557

[rustbot]

r? @TaKO8Ki

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[lqd]

@bors try @rust-timer queue

[bors]

⌛ Trying commit d801a2f with merge add9a3405485dd24dd88b285a65a8cf2b2961aaf...

[bors]

☀️ Try build successful - checks-actions
Build commit: add9a3405485dd24dd88b285a65a8cf2b2961aaf (add9a3405485dd24dd88b285a65a8cf2b2961aaf)

[rust-timer]

Finished benchmarking commit (add9a3405485dd24dd88b285a65a8cf2b2961aaf): comparison URL.

Overall result: no relevant changes - no action needed

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.

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

Instruction count

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

Max RSS (memory usage)

Results

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)	5.2%	[2.4%, 8.1%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

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

Binary size

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

Bootstrap: 632.409s -> 631.435s (-0.15%)

[cjgillot]

Thanks for the fix. I agree this is the cleanest solution.
@bors r+

[bors]

📌 Commit d801a2f has been approved by cjgillot

It is now in the queue for this repository.

[bors]

⌛ Testing commit d801a2f with merge 1e836d1...

[bors]

☀️ Test successful - checks-actions
Approved by: cjgillot
Pushing 1e836d1 to master...

[rust-timer]

Finished benchmarking commit (1e836d1): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.3%, 0.7%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.6%	[-0.8%, -0.5%]	3
All ❌✅ (primary)	0.5%	[0.3%, 0.7%]	2

Max RSS (memory usage)

Results

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)	5.6%	[2.6%, 8.6%]	2
Improvements ✅ (primary)	-2.0%	[-2.0%, -2.0%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.0%	[-2.0%, -2.0%]	1

Cycles

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

Binary size

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

Bootstrap: 632.973s -> 632.609s (-0.06%)

[pnkfelix]

seems like noise

marking as triaged

@rustbot label: +perf-regression-triaged