Don't normalize higher-ranked assumptions if they're not used

[compiler-errors]

See the comment in the code.

Normalizing these assumptions may cause us to register things like new placeholder outlives obligations that cause higher-ranked lifetime errors, and this is problematic if we're not even using these assumptions in borrowck.

Fixes #147244
Fixes #147285

[rustbot]

r? @fee1-dead

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[jackh726]

@bors r+ rollup=never

[bors]

📌 Commit e3f1046 has been approved by jackh726

It is now in the queue for this repository.

[bors]

⌛ Testing commit e3f1046 with merge 7950f24...

[bors]

☀️ Test successful - checks-actions
Approved by: jackh726
Pushing 7950f24 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 595b9a4 (parent) -> 7950f24 (this PR)

Test differences

Show 16 test diffs

Stage 1

• [ui] tests/ui/async-await/higher-ranked-normalize-assumptions-2.rs#hr: [missing] -> pass (J0)
• [ui] tests/ui/async-await/higher-ranked-normalize-assumptions-2.rs#stock: [missing] -> pass (J0)
• [ui] tests/ui/async-await/higher-ranked-normalize-assumptions.rs#hr: [missing] -> pass (J0)
• [ui] tests/ui/async-await/higher-ranked-normalize-assumptions.rs#stock: [missing] -> pass (J0)

Stage 2

• [ui] tests/ui/async-await/higher-ranked-normalize-assumptions-2.rs#hr: [missing] -> pass (J1)
• [ui] tests/ui/async-await/higher-ranked-normalize-assumptions-2.rs#stock: [missing] -> pass (J1)
• [ui] tests/ui/async-await/higher-ranked-normalize-assumptions.rs#hr: [missing] -> pass (J1)
• [ui] tests/ui/async-await/higher-ranked-normalize-assumptions.rs#stock: [missing] -> pass (J1)

Additionally, 8 doctest diffs were found. These are ignored, as they are noisy.

Job group index

• J0: x86_64-gnu-llvm-20-3
• 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-llvm-20, x86_64-gnu-llvm-20-2, 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 7950f244e7ef55b61a83d12f4662be643cd182d6 --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. dist-aarch64-msvc: 5274.6s -> 6397.1s (21.3%)
2. test-various: 4011.5s -> 4749.2s (18.4%)
3. i686-gnu-nopt-1: 7051.7s -> 8138.1s (15.4%)
4. dist-aarch64-apple: 5608.3s -> 6359.8s (13.4%)
5. aarch64-msvc-2: 4604.2s -> 5220.5s (13.4%)
6. aarch64-apple: 9620.4s -> 8432.2s (-12.4%)
7. pr-check-1: 1400.5s -> 1571.3s (12.2%)
8. aarch64-gnu-llvm-20-2: 2153.3s -> 2375.8s (10.3%)
9. x86_64-gnu-tools: 3368.6s -> 3712.1s (10.2%)
10. x86_64-gnu: 6808.1s -> 7455.1s (9.5%)

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 (7950f24): 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)	-0.4%	[-0.6%, -0.3%]	2
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

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

Cycles

Results (primary -2.4%, secondary 1.8%)

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)	1.8%	[1.1%, 2.5%]	2
Improvements ✅ (primary)	-2.4%	[-2.4%, -2.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.4%	[-2.4%, -2.4%]	1

Binary size

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

Bootstrap: 470.682s -> 473.406s (0.58%)
Artifact size: 388.33 MiB -> 388.33 MiB (-0.00%)

[apiraino]

Beta and stable backport accepted as per compiler team on Zulip. A backport PR will be authored by the release team at the end of the current development cycle. Backport labels handled by them.

Stable backport approved as well provided there are plans for a dot release, this alone does not warrant one.

@rustbot label +beta-accepted +stable-accepted