If there are too many suggestions for malformed attribute, do not suggest them

[GuillaumeGomez]

Part of #149865.

This not only covers for doc attributes but for all attributes, so don't hesitate to tell me if you want it to be limited to only doc attributes (although I think it's actually a nice improvement overall).

Also, I picked 3 as the maximum number of suggestions before it becomes noise, but it's very much open to debate.

r? @JonathanBrouwer

[rustbot]

This PR modifies tests/ui/issues/. If this PR is adding new tests to tests/ui/issues/,
please refrain from doing so, and instead add it to more descriptive subdirectories.

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann

[JonathanBrouwer]

r=me when CI is green

[JonathanBrouwer]

@bors r+ rollup

[bors]

📌 Commit d025cde has been approved by JonathanBrouwer

It is now in the queue for this repository.

[GuillaumeGomez]

This one will likely break when put in a rollup so:

@bors p=1 rollup=iffy

[bors]

⌛ Testing commit d025cde with merge fa5eda1...

[bors]

☀️ Test successful - checks-actions
Approved by: JonathanBrouwer
Pushing fa5eda1 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 3391c01 (parent) -> fa5eda1 (this PR)

Test differences

Show 2 test diffs

2 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 fa5eda19b95201468f5b1c5c035ec2fc06fccd66 --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-apple-various: 3173.3s -> 4078.6s (+28.5%)
2. dist-x86_64-musl: 7798.6s -> 6920.8s (-11.3%)
3. dist-aarch64-apple: 7453.6s -> 6693.0s (-10.2%)
4. aarch64-gnu-llvm-20-2: 2504.9s -> 2251.0s (-10.1%)
5. x86_64-msvc-2: 6779.2s -> 7433.7s (+9.7%)
6. dist-x86_64-illumos: 5916.6s -> 6356.9s (+7.4%)
7. dist-x86_64-llvm-mingw: 7217.7s -> 7736.1s (+7.2%)
8. aarch64-gnu-llvm-20-1: 3639.5s -> 3378.5s (-7.2%)
9. x86_64-gnu-llvm-20: 2643.4s -> 2822.9s (+6.8%)
10. x86_64-gnu-aux: 6588.2s -> 7027.9s (+6.7%)

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 (fa5eda1): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (secondary -0.9%)

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)	-0.9%	[-0.9%, -0.9%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -2.1%)

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)	-2.1%	[-2.2%, -2.0%]	2
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 473.663s -> 473.976s (0.07%)
Artifact size: 389.32 MiB -> 389.30 MiB (-0.00%)

[estebank]

I just noticed this and the suggestion machinery already restricts the rendering to the top 4. I am looking at alternative ways of winnowing the number of suggestions by looking at the parts of the existing attribute that were correct already and only include those that change things that need changing. Maybe it would have made sense to provide a link to the docs if we are not presenting a suggestion.

Noticed while doing #154605