Do not eagerly normalize alias during coherence by Shourya742 · Pull Request #157617 · rust-lang/rust

Shourya742 · 2026-06-08T15:33:14Z

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closes: #157407

r? @lcnr

Shourya742 · 2026-06-08T17:35:45Z

~~Moving this to draft~~

rustbot · 2026-06-11T01:02:37Z

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.

Shourya742 · 2026-06-11T07:01:03Z

@bors r=@lcnr

rust-bors · 2026-06-11T07:01:06Z

@Shourya742: 🔑 Insufficient privileges: not in review users

lcnr · 2026-06-11T09:07:58Z

@bors r+ rollup=never

rust-log-analyzer · 2026-06-12T16:52:30Z

A job failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

  IMAGE: dist-x86_64-netbsd
##[endgroup]
    Updating crates.io index
error: failed to get `adler2` as a dependency of package `miniz_oxide v0.8.8`
    ... which satisfies dependency `miniz_oxide = "^0.8.5"` of package `flate2 v1.1.9`
    ... which satisfies dependency `flate2 = "^1.1.9"` of package `citool v0.1.0 (/home/runner/work/rust/rust/src/ci/citool)`

Caused by:
  failed to load source for dependency `adler2`

Caused by:
  unable to update registry `crates-io`

Caused by:
  download of ad/le/adler2 failed

Caused by:
  curl failed

Caused by:

rust-bors · 2026-06-13T03:18:26Z

☀️ Test successful - CI
Approved by: lcnr
Duration: 3h 22m 6s
Pushing 4e391cf to main...

github-actions · 2026-06-13T03:22:05Z

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 6540795 (parent) -> 4e391cf (this PR)

Test differences

Show 5 test diffs

Stage 1

[ui] tests/ui/traits/next-solver/coherence/coherence-unknowable-does-not-eagerly-normalize.rs: [missing] -> pass (J1)
[ui (polonius)] tests/ui/traits/next-solver/coherence/coherence-unknowable-does-not-eagerly-normalize.rs: [missing] -> pass (J2)

Stage 2

[ui] tests/ui/traits/next-solver/coherence/coherence-unknowable-does-not-eagerly-normalize.rs: [missing] -> pass (J0)

Additionally, 2 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 4e391cf2425cf96521af17ff460e9f220e9bca00 --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

x86_64-msvc-ext3: 1h 4m -> 1h 52m (+73.0%)
dist-aarch64-linux: 1h 48m -> 2h 38m (+46.7%)
dist-riscv64-linux: 1h 30m -> 1h (-33.7%)
dist-i686-linux: 1h 49m -> 1h 12m (-33.5%)
dist-x86_64-mingw: 2h 4m -> 2h 38m (+26.6%)
x86_64-msvc-ext1: 2h 24m -> 1h 48m (-25.1%)
optional-x86_64-gnu-parallel-frontend: 2h 40m -> 2h (-24.9%)
dist-x86_64-solaris: 1h 18m -> 1h 35m (+22.1%)
tidy: 2m 29s -> 1m 58s (-20.3%)
x86_64-gnu-gcc-core-tests: 14m 48s -> 12m 18s (-16.9%)

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 · 2026-06-13T03:59:57Z

Finished benchmarking commit (4e391cf): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

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)	0.4%	[0.3%, 0.5%]	6
Regressions ❌ (secondary)	0.4%	[0.3%, 0.5%]	3
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.1%]	4
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	3
All ❌✅ (primary)	0.2%	[-0.3%, 0.5%]	10

Max RSS (memory usage)

Results (primary 1.5%, secondary 6.6%)

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

	mean	range	count
Regressions ❌ (primary)	1.5%	[0.8%, 2.2%]	2
Regressions ❌ (secondary)	6.6%	[6.6%, 6.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[0.8%, 2.2%]	2

Cycles

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

Binary size

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

Bootstrap: 518.069s -> 516.925s (-0.22%)
Artifact size: 401.35 MiB -> 400.84 MiB (-0.13%)

panstromek · 2026-06-16T09:59:16Z

perf triage:

This PR fixes the regression from #155767 and the primary results in nalgebra and diesel looks to be roughly inverse of the results on that PR. It also fixes beta regression, and is part of an important line of work on the type system. Given all that, I think the results are acceptable.

@rustbot label: +perf-regression-triaged

adwinwhite · 2026-06-23T08:27:28Z

The repro minimization probably should be added as a regression test?

lcnr · 2026-06-23T09:56:42Z

The repro minimization probably should be added as a regression test?

what do you mean, we did add tests/ui/traits/next-solver/coherence/coherence-unknowable-does-not-eagerly-normalize.rs as a test. Am I missing another variant here?

adwinwhite · 2026-06-23T10:32:41Z

Never mind. I was too blind to see it.

cuviper · 2026-06-24T23:16:36Z

@jackh726 @lcnr have you discussed this yet as a T-types backport? Please apply the beta-accepted label when you're ready, keeping it nominated too, and I'll take care of it as T-release.

[beta] backports - Do not eagerly normalize alias during coherence #157617 - Don't try to remove assignments in SimplifyComparisonIntegral #158214 r? cuviper

rustbot assigned lcnr Jun 8, 2026

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Shourya742 marked this pull request as draft June 8, 2026 17:35

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 8, 2026

Shourya742 force-pushed the 2026-06-08-donot-eagerly-normalize-alias-during-coherence branch 2 times, most recently from 7ef20cf to 51a1054 Compare June 9, 2026 08:34

Shourya742 marked this pull request as ready for review June 9, 2026 08:44

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 9, 2026

lcnr reviewed Jun 9, 2026

View reviewed changes

Comment thread tests/ui/traits/next-solver/coherence/coherence-unknowable-does-not-eagerly-normalize.rs

lcnr reviewed Jun 9, 2026

View reviewed changes

Comment thread compiler/rustc_trait_selection/src/traits/coherence.rs Outdated

Shourya742 force-pushed the 2026-06-08-donot-eagerly-normalize-alias-during-coherence branch from 51a1054 to 9fa30ac Compare June 9, 2026 12:28

Shourya742 requested a review from lcnr June 9, 2026 13:59

lcnr reviewed Jun 10, 2026

View reviewed changes

Comment thread compiler/rustc_trait_selection/src/traits/coherence.rs Outdated

lcnr changed the title ~~Donot eagerly normalize alias during coherence~~ Do not eagerly normalize alias during coherence Jun 10, 2026

Shourya742 added 4 commits June 11, 2026 06:29

add auxiliary module to define Trait and type in a different crate

6407228

test to see if the coherence fails, when aliases are eagerly normalized

6a6ebb9

make sure to not normalize impl header in coherence

91f63cb

updating other test error types

063fdc0

Shourya742 force-pushed the 2026-06-08-donot-eagerly-normalize-alias-during-coherence branch from 9fa30ac to 063fdc0 Compare June 11, 2026 01:02

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 12, 2026

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rust-bors Bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jun 13, 2026

rust-bors Bot merged commit 4e391cf into rust-lang:main Jun 13, 2026
13 checks passed

rustbot added this to the 1.98.0 milestone Jun 13, 2026

Shourya742 deleted the 2026-06-08-donot-eagerly-normalize-alias-during-coherence branch June 13, 2026 03:45

rustbot added the perf-regression Performance regression. label Jun 13, 2026

This was referenced Jun 15, 2026

[ICE]: failed to resolve instance for <A<[i8; 1]> as From<A<[i8; 1]>>>::from #157937

Open

[ICE]: var types encountered in structurally_relate_consts: ?1c ?1c #157938

Open

rustbot added the perf-regression-triaged The performance regression has been triaged. label Jun 16, 2026

lcnr mentioned this pull request Jun 18, 2026

Add rigid alias marker #156742

Merged

lcnr mentioned this pull request Jun 24, 2026

Stabilize the next-generation trait solver rust-lang/rust-project-goals#113

Open

8 tasks

jackh726 added the beta-accepted Accepted for backporting to the compiler in the beta channel. label Jun 24, 2026

apiraino mentioned this pull request Jun 25, 2026

1.97 beta regression: "conflicting implementations of trait" #157407

Closed

cuviper mentioned this pull request Jun 25, 2026

[beta] backports #158420

Merged

cuviper modified the milestones: 1.98.0, 1.97.0 Jun 25, 2026

cuviper removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Jun 25, 2026

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rustbot commented Jun 11, 2026

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github-actions Bot commented Jun 13, 2026

Test differences

Stage 1

Stage 2

Job duration changes

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rust-timer commented Jun 13, 2026

Overall result: ❌✅ regressions and improvements - please read:

Instruction count

Max RSS (memory usage)

Cycles

Binary size

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panstromek commented Jun 16, 2026

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adwinwhite commented Jun 23, 2026

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lcnr commented Jun 23, 2026

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adwinwhite commented Jun 23, 2026

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cuviper commented Jun 24, 2026

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Shourya742 commented Jun 8, 2026 •

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