Remove structural match from TypeId

[raldone01]

As per #99189 (comment).

Removing the structural equality might make sense, but is a breaking change that'd require a libs-api FCP.

#99189 (comment)

Landing this PR now (well, mainly the "remove structural equality" part) would unblock const fn TypeId::of, since we only postponed that because we were guaranteeing too much.

See also #99189, #101698

[rust-highfive]

r? @thomcc

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[rustbot]

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

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[thomcc]

I can't start that FCP and the comment is from @m-ou-se so....

r? @m-ou-se

[raldone01]

@rustbot label +T-libs-api -T-libs

[onestacked]

cc @m-ou-se @eddyb

[onestacked]

@rustbot label +needs-fcp

[eddyb]

LGTM but I don't understand what's going on with the test.

[eddyb]

Marking as blocked on:

• Constify TypeId ordering impls #101698

[raldone01]

@rustbot ready

[WaffleLapkin]

Is this waiting on libs FCP to be started?

[onestacked]

@m-ou-se and @eddyb wanted this, so i think yes.

[bors]

☔ The latest upstream changes (presumably #110393) made this pull request unmergeable. Please resolve the merge conflicts.

[dtolnay]

@bors r+

[bors]

📌 Commit 6827a41 has been approved by dtolnay

It is now in the queue for this repository.

[bors]

⌛ Testing commit 6827a41 with merge 1a5f8bc...

[rfcbot]

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

[bors]

☀️ Test successful - checks-actions
Approved by: dtolnay
Pushing 1a5f8bc to master...

[dtolnay]

The pinnacle of efficiency. This must be a record?

[rust-timer]

Finished benchmarking commit (1a5f8bc): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.1%	[-2.8%, -1.4%]	2
All ❌✅ (primary)	-	-	0

Cycles

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)	3.2%	[2.1%, 4.8%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 643.928s -> 644.897s (0.15%)

[jackh726]

sorry to necro this a bit - looking through our I-unsound known-bug tracking in #105107 and came across this.

@dtolnay I added a commit that blesses the tests, but test tests/ui/const-generics/generic_const_exprs/typeid-equality-by-subtyping.rs uses Structural match of TypeId, so i removed the // run-pass and added #110395 as known-bug since comparing TypeId in const context is now imposible.

I'm not sure if this is how this should be done, since there was already a I-unsound related known bug on this test.

For future reference: this is not the correct use of known-bug. #110395 is not a bug for one. This obviously was resolved over time, but in the future please tag the appropriate team (in this case T-types) to check what the appropriate course is for handling changes to known-bug cases (you could imagine, for example, that an alternative resolution would be that #97156 could have been closed with this PR).