outline unreachable! from Clause::kind

[panstromek]

Safe alternative to #163639. unreachable!() expands to panic("internal error: entered unreachable code"), which we've seen before to be worse than plain argument-less call in other hot places.

see https://rust-lang.zulipchat.com/#narrow/channel/247081-t-compiler.2Fperformance/topic/needs.20help.3A.20small.20perf.20improvement.20with.20non-local.20reasoning/with/628660586

[panstromek]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 2660fea (2660fea4cf8b7dcc478d2dc474f57411892974f5)
Base parent: c165834 (c1658342b0ea7eab61db1960082668c77f553522)

[rust-timer]

Finished benchmarking commit (2660fea): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

@bors rollup=never rustc-perf
@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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.4%	[-0.6%, -0.1%]	4
Improvements ✅ (secondary)	-0.4%	[-0.7%, -0.2%]	34
All ❌✅ (primary)	-0.4%	[-0.6%, -0.1%]	4

Max RSS (memory usage)

Results (secondary 3.9%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.9%	[3.9%, 3.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (primary 2.4%, secondary 3.0%)

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

	mean	range	count
Regressions ❌ (primary)	2.4%	[2.1%, 2.7%]	2
Regressions ❌ (secondary)	3.0%	[3.0%, 3.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.4%	[2.1%, 2.7%]	2

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 491.121s -> 490.2s (-0.19%)
Artifact size: 408.64 MiB -> 408.63 MiB (-0.00%)

[rustbot]

r? @oli-obk

rustbot has assigned @oli-obk.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: compiler, types
• compiler, types expanded to 77 candidates
• Random selection from 19 candidates

[panstromek]

This is not as good as unreachable_unchecked but it's at least something.

[lcnr]

can you put a comment here referencing this perf run, r=me after

View changes since the review

[panstromek]

Done, thanks ;) but I don't have r+ rights to approve this

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[lcnr]

@bors r+ rollup=never

[rust-bors]

📌 Commit 22f30e6 has been approved by lcnr

It is now in the queue for this repository.