Better closure requirement propagation.

[LorrensP-2158466]

Fixes #148289
Fixes #104477
Should unblock #148187

When propagating closure requirements we:

• no longer try to find a post dominiting region for the list of non-local lower bounds of longer_fr.
• we filter the list of longer_fr-: shorter_fr+ to only these constraints between external regions which are required regardless. If no such constraint exists, we fall back to propagating all of them.

See the FCP for more information.

r? @lcnr

[rustbot]

Some changes occurred in src/tools/cargo

cc @ehuss

[LorrensP-2158466]

Excuse me ehuss for the automatic ping, I was a bit too fast with pushing the typo fixes reported by the tidy job.

[lcnr]

@bors try @rust-timer

let's do a crater run, even if I think it should be fine. Then I/we need to write an FCP proposal 😁

[LorrensP-2158466]

let's do a crater run, even if I think it should be fine. Then I/we need to write an FCP proposal 😁

Alright!

[LorrensP-2158466]

Then I/we need to write an FCP proposal 😁

BTW, I would love to help with this if isn't to much to ask. I have never done it, so I might as well get some experience. :)

[rust-bors]

☀️ Try build successful (CI)
Build commit: f27166d (f27166d4c64dc29edc5ea3214357f191edf8b635, parent: f5711a55f5d5e2f942057d0f6d648dd2d8b2c37b)

[lcnr]

@craterbot check

[craterbot]

👌 Experiment pr-148329 created and queued.
🤖 Automatically detected try build f27166d
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[Kobzol]

@rust-timer build f27166d

[rust-timer]

Finished benchmarking commit (f27166d): comparison URL.

Overall result: no relevant changes - no action needed

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.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

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

Max RSS (memory usage)

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

Cycles

Results (secondary -4.7%)

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.7%	[-5.4%, -4.0%]	2
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 474.205s -> 473.796s (-0.09%)
Artifact size: 390.90 MiB -> 390.90 MiB (0.00%)

[craterbot]

🚧 Experiment pr-148329 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[bors]

📌 Commit 0627df9 has been approved by lcnr

It is now in the queue for this repository.

[LorrensP-2158466]

Okey, Yeah... I'm sorry, I misunderstood what you said. I feel like what I did in [this comment](#t-types > work on FCP proposal for closure requirements @ 💬) Was the correct way, if you look in those pasted lists, you'll see the tests you added in the proposal.
When you responded on that message, I completely missed your point, and thought you wanted a new test that demonstrated both behaviours.

This is on me 😞.

[bors]

⌛ Testing commit 0627df9 with merge cb79c42...

[bors]

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing cb79c42 to main...

[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 24139cf (parent) -> cb79c42 (this PR)

Test differences

Show 12 test diffs

Stage 1

• [ui] tests/ui/nll/closure-requirements/propagate-approximated-both-lower-bounds.rs: [missing] -> pass (J0)
• [ui] tests/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.rs: pass -> [missing] (J0)
• [ui] tests/ui/regions/closure-prop-issue-104477-case1.rs: [missing] -> pass (J0)
• [ui] tests/ui/regions/closure-prop-issue-104477-case2.rs: [missing] -> pass (J0)
• [ui] tests/ui/regions/closure-prop-issue-148289.rs: [missing] -> pass (J0)

Stage 2

• [ui] tests/ui/nll/closure-requirements/propagate-approximated-both-lower-bounds.rs: [missing] -> pass (J1)
• [ui] tests/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.rs: pass -> [missing] (J1)
• [ui] tests/ui/regions/closure-prop-issue-104477-case1.rs: [missing] -> pass (J1)
• [ui] tests/ui/regions/closure-prop-issue-104477-case2.rs: [missing] -> pass (J1)
• [ui] tests/ui/regions/closure-prop-issue-148289.rs: [missing] -> pass (J1)

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

Job group index

• J0: x86_64-gnu-llvm-20-3, x86_64-gnu-llvm-21-3
• J1: aarch64-apple, aarch64-gnu, aarch64-gnu-llvm-20-1, aarch64-msvc-1, arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, test-various, x86_64-gnu, x86_64-gnu-debug, x86_64-gnu-gcc, x86_64-gnu-llvm-20, x86_64-gnu-llvm-20-2, x86_64-gnu-llvm-21-2, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard cb79c42008b970269f6a06b257e5f04b93f24d03 --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. aarch64-apple: 12930.0s -> 8913.4s (-31.1%)
2. test-various: 6785.3s -> 7968.9s (+17.4%)
3. x86_64-gnu-llvm-20: 4772.5s -> 4092.8s (-14.2%)
4. aarch64-gnu-debug: 4422.2s -> 3793.1s (-14.2%)
5. dist-aarch64-msvc: 6447.3s -> 5575.3s (-13.5%)
6. armhf-gnu: 5542.6s -> 4866.9s (-12.2%)
7. dist-x86_64-apple: 7449.4s -> 6543.0s (-12.2%)
8. aarch64-gnu: 7995.4s -> 7040.2s (-11.9%)
9. dist-ohos-x86_64: 4785.5s -> 4239.4s (-11.4%)
10. aarch64-gnu-llvm-20-1: 3619.0s -> 3216.9s (-11.1%)

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 (cb79c42): comparison URL.

Overall result: ❌ regressions - 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)	0.1%	[0.1%, 0.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 2.1%, 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)	2.1%	[2.0%, 2.1%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.5%	[-1.5%, -1.5%]	1
All ❌✅ (primary)	2.1%	[2.0%, 2.1%]	2

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: 480.029s -> 482.897s (0.60%)
Artifact size: 390.62 MiB -> 390.62 MiB (-0.00%)