Region inference: Use outlives-static constraints in constraint search #140737

amandasystems · 2025-05-07T11:12:09Z

Revise the extra r: 'static constraints added upon universe issues to add an explanation, and use that explanation during constraint blame search. This greatly simplifies the region inference logic, which now does not need to reverse-engineer the event that caused a region to outlive 'static.

This cosmetically changes the output of two UI tests. I blessed them i separate commits with separate motivations, but that can of course be squashed as desired. We probably want that.

The PR was extracted out of #130227 and consists of one-third of its functional payload.

r? lcnr

bors · 2025-06-05T09:38:19Z

☔ The latest upstream changes (presumably #140466) made this pull request unmergeable. Please resolve the merge conflicts.

amandasystems · 2025-06-09T11:48:37Z

(We may also want a perf run to see if I messed something up badly)

lcnr · 2025-06-09T11:49:59Z

@bors try @rust-timer queue

Region inference: Use outlives-static constraints in constraint search Revise the extra `r: 'static` constraints added upon universe issues to add an explanation, and use that explanation during constraint blame search. This greatly simplifies the region inference logic, which now does not need to reverse-engineer the event that caused a region to outlive `'static`. This cosmetically changes the output of two UI tests. I blessed them i separate commits with separate motivations, but that can of course be squashed as desired. We probably want that. The PR was extracted out of #130227 and consists of one-third of its functional payload. It is based on #140466, so that has to land first. We probably want a perf run of this. It shouldn't have much of an impact and a positive one if any, but I have been wrong before. In particular, SCC annotations are heavier now. r? lcnr

bors · 2025-06-09T11:51:10Z

⌛ Trying commit a209255 with merge 0d3d480...

bors · 2025-06-09T14:19:00Z

☀️ Try build successful - checks-actions
Build commit: 0d3d480 (0d3d48082efe47a20c953415945cc721105e5f85)

rust-timer · 2025-06-09T15:46:52Z

Finished benchmarking commit (0d3d480): 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)	0.2%	[0.1%, 0.3%]	12
Regressions ❌ (secondary)	0.2%	[0.1%, 0.3%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.5%	[-0.6%, -0.5%]	6
All ❌✅ (primary)	0.2%	[0.1%, 0.3%]	12

Max RSS (memory usage)

Results (primary 0.4%, secondary -1.0%)

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

	mean	range	count
Regressions ❌ (primary)	1.4%	[1.3%, 1.5%]	2
Regressions ❌ (secondary)	3.0%	[3.0%, 3.0%]	1
Improvements ✅ (primary)	-1.7%	[-1.7%, -1.7%]	1
Improvements ✅ (secondary)	-1.9%	[-2.4%, -0.6%]	4
All ❌✅ (primary)	0.4%	[-1.7%, 1.5%]	3

Cycles

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

Binary size

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

Bootstrap: 753.257s -> 756.017s (0.37%)
Artifact size: 372.34 MiB -> 372.33 MiB (-0.00%)

bors · 2025-08-21T07:39:33Z

☔ The latest upstream changes (presumably #145244) made this pull request unmergeable. Please resolve the merge conflicts.

compiler/rustc_borrowck/src/handle_placeholders.rs

compiler/rustc_borrowck/src/region_infer/mod.rs

lcnr · 2025-08-22T10:20:55Z

needs rebase :>

Revise the extra `r: 'static` constraints added upon universe issues to add an explanation, and use that explanation during constraint blame search. This greatly simplifies the region inference logic, which now does not need to reverse-engineer the event that caused a region to outlive 'static.

rustbot · 2025-08-22T11:38:54Z

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.

rework GAT borrowck limitation error The old one depends on the `ConstraintCategory` of the constraint which meant we did not emit this note if we had to prove the higher ranked trait bound due to e.g. normalization. This made it annoying brittle and caused MIR borrowck errors to be order dependent, fixes the issue in rust-lang/rust#140737 (comment). r? types cc ```@amandasystems```

lcnr · 2025-08-25T09:12:06Z

@bors r+ rollup=never

bors · 2025-08-25T09:12:09Z

📌 Commit ae622bb has been approved by lcnr

It is now in the queue for this repository.

Region inference: Use outlives-static constraints in constraint search Revise the extra `r: 'static` constraints added upon universe issues to add an explanation, and use that explanation during constraint blame search. This greatly simplifies the region inference logic, which now does not need to reverse-engineer the event that caused a region to outlive `'static`. This cosmetically changes the output of two UI tests. I blessed them i separate commits with separate motivations, but that can of course be squashed as desired. We probably want that. The PR was extracted out of #130227 and consists of one-third of its functional payload. r? lcnr

bors · 2025-08-25T13:50:37Z

⌛ Testing commit ae622bb with merge 5039e79...

bors · 2025-08-25T15:26:37Z

💔 Test failed - checks-actions

amandasystems · 2025-08-26T17:23:23Z

💔 Test failed - checks-actions

That seems pretty spurious?

lcnr · 2025-08-27T07:26:45Z

@bors retry

bors · 2025-08-27T09:25:50Z

⌛ Testing commit ae622bb with merge b2dd217...

bors · 2025-08-27T12:34:13Z

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing b2dd217 to master...

github-actions · 2025-08-27T12:37:08Z

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 4f808ba (parent) -> b2dd217 (this PR)

Test differences

Show 17 test diffs

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

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard b2dd217dd0a099fb87601657ec480bf3e92b30a6 --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-apple: 7951.7s -> 5817.1s (-26.8%)
aarch64-apple: 6291.0s -> 5039.7s (-19.9%)
x86_64-gnu-llvm-19-1: 3151.8s -> 3626.4s (15.1%)
pr-check-1: 1377.1s -> 1566.8s (13.8%)
aarch64-gnu-debug: 4228.9s -> 4806.5s (13.7%)
dist-x86_64-apple: 7135.3s -> 8068.7s (13.1%)
x86_64-gnu-llvm-19: 2458.6s -> 2770.9s (12.7%)
i686-msvc-2: 7715.8s -> 8490.5s (10.0%)
x86_64-gnu-distcheck: 5083.6s -> 5510.5s (8.4%)
test-various: 4664.6s -> 5047.5s (8.2%)

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 · 2025-08-27T14:00:18Z

Finished benchmarking commit (b2dd217): comparison URL.

Overall result: ❌✅ regressions and improvements - 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)	0.2%	[0.1%, 0.4%]	13
Regressions ❌ (secondary)	0.2%	[0.1%, 0.3%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.3%]	6
All ❌✅ (primary)	0.2%	[0.1%, 0.4%]	13

Max RSS (memory usage)

Results (primary 0.3%, 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)	1.5%	[1.5%, 1.5%]	1
Regressions ❌ (secondary)	2.3%	[2.3%, 2.3%]	1
Improvements ✅ (primary)	-0.9%	[-0.9%, -0.9%]	1
Improvements ✅ (secondary)	-4.3%	[-5.2%, -2.9%]	5
All ❌✅ (primary)	0.3%	[-0.9%, 1.5%]	2

Cycles

Results (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)	-	-	0
Regressions ❌ (secondary)	2.7%	[2.3%, 3.4%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 467.222s -> 468.683s (0.31%)
Artifact size: 391.17 MiB -> 391.17 MiB (-0.00%)

rustbot assigned lcnr May 7, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels May 7, 2025

amandasystems force-pushed the revised-constraint-search branch from f4af776 to 72e81ea Compare May 16, 2025 10:14

amandasystems mentioned this pull request May 26, 2025

Move placeholder handling to a proper preprocessing step #140466

Merged

amandasystems force-pushed the revised-constraint-search branch from 72e81ea to 9a1face Compare May 27, 2025 10:09