attempt to fix unreachable code regression

[Kivooeo]

For some reason it works, it checks function output type and suppress warning if type is uninhabited

This double negations in code breaks my mind actually

I'd love to revisit this part in future and try to find a proper solution maybe, but for now I feel like it's enough before release to fix the issue? I really wonder what team does think, especially @cjgillot and other people who are more confident in this part of compiler than I do

I tried a lot of things here, it's only approach that pass all tests included new regression one

fixes #149571

r? compiler

[apiraino]

PR has been just opened so probably still early to evaluate a backport but I'll add the nomination just in case, so we don't overlook this patch - we're getting very close to the release deadline.

Thank you @Kivooeo !

@rustbot label beta-nominated

[davidtwco]

r=me after fixing nit

View changes since this review

[Kivooeo]

@bors r=davidtwco

[bors]

📌 Commit 2a2da78 has been approved by davidtwco

It is now in the queue for this repository.

[apiraino]

Beta backport accepted as per compiler team on Zulip. A backport PR will be authored by the release team at the end of the current development cycle. Backport labels handled by them.

(As the milestone label implies, this is a backport for 1.93)

@rustbot label +beta-accepted

[Kobzol]

@rust-timer build 2fe9b51

Trying if this regressed perf. in #149818.

[rust-timer]

Finished benchmarking commit (2fe9b51): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

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

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.2%, 0.3%]	16
Regressions ❌ (secondary)	0.3%	[0.2%, 0.5%]	14
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.2%, 0.3%]	16

Max RSS (memory usage)

Results (primary 1.4%, secondary 1.3%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.4%	[1.4%, 1.4%]	1
Regressions ❌ (secondary)	1.3%	[1.3%, 1.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.4%	[1.4%, 1.4%]	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: 471.772s -> 476.618s (1.03%)
Artifact size: 389.00 MiB -> 389.02 MiB (0.01%)

[Kobzol]

It seems like this caused a perf. regression. Do you think something could be done to reduce it?

[Kivooeo]

Hmm, I think that I can try (not sure if it help or not)

What will happen if I push changes to this merged branch?

[Kobzol]

That's not really useful for anything, it should be a new PR :)