Canonicalize free regions from inputs as placeholders in root univ by ShoyuVanilla · Pull Request #155487 · rust-lang/rust

ShoyuVanilla · 2026-04-18T15:04:43Z

Context: The box named coroutine witness Send lifetime requirements now considered by leakcheck this roadmap

Fixes (only for the next-solver) #106569
Prerequisite of #155749

ShoyuVanilla · 2026-04-18T15:05:15Z

Canonicalize free regions from inputs as placeholders in root univ

rust-bors · 2026-04-18T17:13:45Z

☀️ Try build successful (CI)
Build commit: e39d9d1 (e39d9d1e2232da07330c87d8314c3587ec4edb1f, parent: 8da2d28cbd5a4e2b93e028e709afe09541671663)

rust-timer · 2026-04-18T17:54:32Z

Finished benchmarking commit (e39d9d1): 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
@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)	0.2%	[0.1%, 0.3%]	4
Improvements ✅ (primary)	-1.1%	[-4.4%, -0.2%]	40
Improvements ✅ (secondary)	-1.1%	[-3.2%, -0.1%]	33
All ❌✅ (primary)	-1.1%	[-4.4%, -0.2%]	40

Max RSS (memory usage)

Results (primary 2.8%, secondary 3.2%)

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

	mean	range	count
Regressions ❌ (primary)	2.8%	[1.0%, 5.5%]	7
Regressions ❌ (secondary)	3.2%	[1.6%, 4.8%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.8%	[1.0%, 5.5%]	7

Cycles

Results (primary -3.2%, secondary 0.2%)

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)	2.1%	[2.1%, 2.1%]	1
Improvements ✅ (primary)	-3.2%	[-4.0%, -2.3%]	7
Improvements ✅ (secondary)	-1.6%	[-1.6%, -1.6%]	1
All ❌✅ (primary)	-3.2%	[-4.0%, -2.3%]	7

Binary size

Results (secondary -0.1%)

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	4
All ❌✅ (primary)	-	-	0

Bootstrap: 493.313s -> 494.404s (0.22%)
Artifact size: 394.36 MiB -> 394.31 MiB (-0.01%)

ShoyuVanilla · 2026-04-19T08:07:12Z

r? lcnr

ShoyuVanilla · 2026-04-19T08:10:26Z

-   = note: closure with signature `for<'a> fn(&'a &'2 str) -> bool` must implement `FnOnce<(&&'1 str,)>`, for any lifetime `'1`...
-   = note: ...but it actually implements `FnOnce<(&&'2 str,)>`, for some specific lifetime `'2`
+   = note: closure with signature `for<'a> fn(&'a &'0 str) -> bool` must implement `FnOnce<(&&'1 str,)>`, for any two lifetimes `'0` and `'1`...
+   = note: ...but it actually implements `FnOnce<(&&str,)>`


We have lots of those ...but it actually implements X for some specific lifetime '?x -> ...but it actually implements X for some specific lifetime diagnostic drifts due to the canonicalized region being placeholders rather than region vars.
I think this is somewhat regressive. Would it make sense to fix them somehow?

View changes since the review

ShoyuVanilla · 2026-04-27T04:43:26Z

I'm not sure I should do something with diagnostics but marking this as ready 😅

lcnr · 2026-04-27T08:26:09Z

+                    if !(placeholder.universe() == ty::UniverseIndex::ROOT
+                        && placeholder.bound.kind == ty::BoundRegionKind::Anon)
+                        && max_input_universe.can_name(placeholder.universe())


shouldn't just placeholder.universe() != ty::UniverseIndex::ROOT be enough here. We should never add new placeholders to an existing universe and max_input_universe is guaranteed to be able to the root universe, as can_name is equivalent to max_input_universe >= placeholder.universe()

View changes since the review

Wouldn't there still be the cases that adding new placeholders to a new_universe > max_input_universe?

ah, yeah, it's the other way around

either the placeholder is in the root universe

or from a universe which can't be named by max_input_universe

lcnr

2 thoughts here:

It's somewhat scary that this requires literally no changes when we instantiate query responses. I guess what's happening is that this is (another) load bearing use of query_response_instantiation_guess (old solver) and the hack in compute_query_response_instantiation_values (next solver). We should definitely at least update the comments here.

Related to the above, it feels scary to me to change the old solver canonicalization here. I think your change also makes the different CanonicalizeMode be slightly outdated or what not 🤔 could you just limit this to the new solver for now?

CanonicalizeUserTypeAnnotations is interesting to me as that one is more a canonicalize_response where the var_values are just the early/late bound params in the parent function

View changes since this review

ShoyuVanilla · 2026-04-27T16:13:10Z

@bors try @rust-timer queue

ShoyuVanilla · 2026-04-28T23:17:42Z

@bors r=lcnr

rust-bors · 2026-04-28T23:17:45Z

📌 Commit 926a31b has been approved by lcnr

It is now in the queue for this repository.

Canonicalize free regions from inputs as placeholders in root univ Context: The box named *coroutine witness Send lifetime requirements now considered by leakcheck* [this roadmap](https://raw.githubusercontent.com/hexcatnl/roadmap/e380fef94b47c02a056b4c8f05124a9db475b990/next-solver.svg) Fixes (only for the next-solver) #106569 Prerequisite of #155749

rust-bors · 2026-04-29T04:15:01Z

💔 Test for 976cee2 failed: CI. Failed job:

auto - dist-x86_64-msvc (web logs, enhanced plaintext logs)

rustbot · 2026-04-29T04:15:22Z

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.

ShoyuVanilla · 2026-04-29T04:15:34Z

@bors r=lcnr

rust-bors · 2026-04-29T04:15:37Z

📌 Commit f2ae894 has been approved by lcnr

It is now in the queue for this repository.

rust-bors · 2026-04-29T16:57:50Z

☀️ Test successful - CI
Approved by: lcnr
Duration: 3h 40m 1s
Pushing c935696 to main...

github-actions · 2026-04-29T17:00:33Z

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 0424cc1 (parent) -> c935696 (this PR)

Test differences

Show 9 test diffs

Stage 1

[ui] tests/ui/implied-bounds/normalization-preserve-equality.rs#borrowck: pass -> [missing] (J1)
[ui] tests/ui/implied-bounds/normalization-preserve-equality.rs#borrowck_current: [missing] -> pass (J1)
[ui] tests/ui/implied-bounds/normalization-preserve-equality.rs#borrowck_next: [missing] -> pass (J1)

Stage 2

[ui] tests/ui/implied-bounds/normalization-preserve-equality.rs#borrowck: pass -> [missing] (J0)
[ui] tests/ui/implied-bounds/normalization-preserve-equality.rs#borrowck_current: [missing] -> pass (J0)
[ui] tests/ui/implied-bounds/normalization-preserve-equality.rs#borrowck_next: [missing] -> pass (J0)

Additionally, 3 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 c935696dd07ca51e6fba2f6579919eea2a50863b --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

dist-aarch64-linux: 1h 47m -> 2h 58m (+66.2%)
dist-x86_64-illumos: 1h 37m -> 2h 39m (+63.7%)
dist-x86_64-llvm-mingw: 1h 29m -> 2h 17m (+54.2%)
dist-ohos-armv7: 1h 8m -> 1h 37m (+43.6%)
dist-ohos-x86_64: 1h 14m -> 1h 47m (+43.3%)
dist-x86_64-freebsd: 1h 24m -> 1h 59m (+41.0%)
dist-ohos-aarch64: 1h 17m -> 1h 48m (+40.1%)
dist-aarch64-llvm-mingw: 1h 39m -> 2h 3m (+24.2%)
dist-x86_64-mingw: 2h 10m -> 2h 37m (+20.8%)
dist-i686-linux: 1h 51m -> 2h 13m (+19.8%)

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 · 2026-04-29T17:39:17Z

Finished benchmarking commit (c935696): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -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
Improvements ✅ (secondary)	-1.2%	[-2.9%, -0.8%]	6
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary 0.2%)

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)	1.6%	[1.6%, 1.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.3%	[-1.3%, -1.3%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -0.3%)

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)	2.3%	[2.3%, 2.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.9%	[-2.9%, -2.9%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 481.379s -> 487.214s (1.21%)
Artifact size: 390.96 MiB -> 390.94 MiB (-0.01%)

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rust-bors Bot pushed a commit that referenced this pull request Apr 18, 2026

Auto merge of #155487 - ShoyuVanilla:canon-ph, r=<try>

e39d9d1

Canonicalize free regions from inputs as placeholders in root univ

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 18, 2026

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 18, 2026

ShoyuVanilla force-pushed the canon-ph branch 2 times, most recently from 3b462e7 to bfdd538 Compare April 19, 2026 07:50

rustbot assigned lcnr Apr 19, 2026

ShoyuVanilla commented Apr 19, 2026

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ShoyuVanilla mentioned this pull request Apr 24, 2026

-Znext-solver Ignore region constraints from the nested goals in leakcheck #155749

Merged

ShoyuVanilla marked this pull request as ready for review April 27, 2026 04:43

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 Apr 27, 2026

lcnr reviewed Apr 27, 2026

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ShoyuVanilla force-pushed the canon-ph branch from bfdd538 to 88c34ea Compare April 27, 2026 16:02

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ShoyuVanilla force-pushed the canon-ph branch 2 times, most recently from da3a195 to 7f82ec1 Compare April 27, 2026 16:05

ShoyuVanilla force-pushed the canon-ph branch from 7f82ec1 to 926a31b Compare April 28, 2026 17:30

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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 Apr 28, 2026

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Canonicalize free regions from inputs as placeholders in root univ

f2ae894

rust-bors Bot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Apr 29, 2026

ShoyuVanilla force-pushed the canon-ph branch from 926a31b to f2ae894 Compare April 29, 2026 04:15

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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 Apr 29, 2026

rust-bors Bot merged commit c935696 into rust-lang:main Apr 29, 2026
12 checks passed

rustbot added this to the 1.97.0 milestone Apr 29, 2026

ShoyuVanilla deleted the canon-ph branch April 29, 2026 17:22

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Overall result: ✅ improvements - no action needed

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Test differences

Stage 1

Stage 2

Job duration changes

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rust-timer commented Apr 29, 2026

Overall result: ✅ improvements - no action needed

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