Split transmute check from HIR typeck

[cjgillot]

This resolves a FIXME in the implementation of check_transmute.

check_transmute needs to compute type layout, hence needing to see reveal opaques and all type aliases.
Having this inside typeck causes a cycle. For instance: tests/ui/impl-trait/transmute/in-defining-scope.rs.

This PR moves the transmute check outside of typeck, by putting the list of deferred transmute checks in typeck results.

[rustbot]

r? @nnethercote

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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

[cjgillot]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 531f732 (531f732ba93e69ac09e8bc77d95a54d701e72e84, parent: cd7cbe818e4a66d46fe2df993d1b8518eba8a5cd)

[rust-timer]

Finished benchmarking commit (531f732): comparison URL.

Overall result: ❌✅ regressions and improvements - 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)	0.5%	[0.2%, 3.3%]	16
Regressions ❌ (secondary)	0.6%	[0.3%, 1.0%]	10
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.5%	[-1.1%, -0.1%]	4
All ❌✅ (primary)	0.5%	[0.2%, 3.3%]	16

Max RSS (memory usage)

Results (primary 2.1%, secondary 6.5%)

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

	mean	range	count
Regressions ❌ (primary)	2.1%	[0.4%, 6.8%]	4
Regressions ❌ (secondary)	9.4%	[7.2%, 12.3%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.5%	[-2.5%, -2.5%]	1
All ❌✅ (primary)	2.1%	[0.4%, 6.8%]	4

Cycles

Results (primary 2.7%, secondary 2.7%)

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

	mean	range	count
Regressions ❌ (primary)	2.7%	[2.7%, 2.7%]	1
Regressions ❌ (secondary)	2.7%	[2.2%, 3.6%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.7%	[2.7%, 2.7%]	1

Binary size

Results (primary 0.6%, secondary -1.5%)

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

	mean	range	count
Regressions ❌ (primary)	0.6%	[0.6%, 0.6%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.5%	[-1.5%, -1.5%]	1
All ❌✅ (primary)	0.6%	[0.6%, 0.6%]	1

Bootstrap: 469.562s -> 470.22s (0.14%)
Artifact size: 377.55 MiB -> 377.50 MiB (-0.01%)

[nnethercote]

Nothing wrong that I can see and some of the test outcomes are clearly better. Having said that I am very unfamiliar with this code and it's not an easy PR to review (awkward diffs) so my r+ has a heavy sprinkling of "I trust you know what you're doing".

@bors r+

[bors]

📌 Commit f4137ad has been approved by nnethercote

It is now in the queue for this repository.

[Zalathar]

Scheduling: Prefer a rollup=never PR over rollup=iffy ones that aren't rolled up.

@bors p=1

[bors]

⌛ Testing commit f4137ad with merge 3bf318c...

[bors]

💔 Test failed - checks-actions

[rustbot]

This PR was rebased onto a different master 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.

[cjgillot]

@bors r=nnethercote

[bors]

📌 Commit 0327e2b has been approved by nnethercote

It is now in the queue for this repository.

[bors]

⌛ Testing commit 0327e2b with merge 78b89eb...

[bors]

☀️ Test successful - checks-actions
Approved by: nnethercote
Pushing 78b89eb to master...

[github-actions]

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 6545b05 (parent) -> 78b89eb (this PR)

Test differences

Show 49 test diffs

Stage 2

• [ui] tests/rustdoc-ui/issues/issue-79494.rs: ignore (only executed when the target is x86_64-unknown-linux-gnu) -> ignore (only executed when the pointer width is 64bit) (J0)
• [ui] tests/rustdoc-ui/issues/issue-79494.rs: ignore (only executed when the target is x86_64-unknown-linux-gnu) -> pass (J1)

Additionally, 47 doctest diffs were found. These are ignored, as they are noisy.

Job group index

• J0: i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1
• J1: aarch64-apple, aarch64-gnu, aarch64-gnu-llvm-19-1, aarch64-msvc-1, x86_64-mingw-1, x86_64-msvc-1

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 78b89ebb6b20cf50370335e14c5357a4388ac760 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

1. pr-check-1: 1726.9s -> 1325.2s (-23.3%)
2. dist-aarch64-apple: 6212.9s -> 5285.9s (-14.9%)
3. dist-x86_64-apple: 7615.1s -> 6651.6s (-12.7%)
4. pr-check-2: 2413.5s -> 2191.0s (-9.2%)
5. aarch64-apple: 6449.0s -> 5872.6s (-8.9%)
6. dist-aarch64-msvc: 5570.1s -> 6056.2s (8.7%)
7. x86_64-gnu-llvm-20-1: 3362.3s -> 3635.3s (8.1%)
8. aarch64-gnu-llvm-19-1: 3867.4s -> 3561.2s (-7.9%)
9. dist-powerpc64le-linux-gnu: 5145.3s -> 5496.9s (6.8%)
10. x86_64-rust-for-linux: 2704.0s -> 2888.2s (6.8%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

[rust-timer]

Finished benchmarking commit (78b89eb): comparison URL.

Overall result: ❌ regressions - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

• If the regression was expected or you think it can be justified,
  please write a comment with sufficient written justification, and add
  @rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
• If you think that you know of a way to resolve the regression, try to create
  a new PR with a fix for the regression.
• If you do not understand the regression or you think that it is just noise,
  you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
  were already notified of this PR).

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

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)	0.6%	[0.6%, 0.6%]	1
Regressions ❌ (secondary)	0.8%	[0.6%, 1.0%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.6%	[0.6%, 0.6%]	1

Max RSS (memory usage)

Results (primary 4.5%, secondary 7.7%)

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

	mean	range	count
Regressions ❌ (primary)	4.5%	[2.1%, 6.9%]	2
Regressions ❌ (secondary)	7.7%	[2.3%, 12.2%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	4.5%	[2.1%, 6.9%]	2

Cycles

Results (primary 2.3%)

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

	mean	range	count
Regressions ❌ (primary)	2.3%	[2.3%, 2.3%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.3%	[2.3%, 2.3%]	1

Binary size

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

Bootstrap: 467.563s -> 467.345s (-0.05%)
Artifact size: 378.27 MiB -> 378.27 MiB (0.00%)

[panstromek]

perf triage:

Are the regressions here justified? I see the PR was already a regression before merge (#145469 (comment)), but no other comment on that. The final regression is smaller and mostly affects a secondary stress test, but I'm asking to make sure it's not an oversight.