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[unnecessary_safety_comment] Some fixes regarding comments above attributes #15678

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[unnecessary_safety_comment] Some fixes regarding comments above attributes #15678

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@teofr teofr commented Sep 15, 2025 •
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The way clippy checked for SAFETY comments above attributes was wrong:

  • It wasn't considered for items
  • It cause an ICE with some attributes
  • When considering comments above attributes, it didn't considered comments below them, causing some unlintable situations.

This PR tries to fix this by delegating the skipping of attributes to the function analyzing the source code itself.

changelog: [unnecessary_safety_comment]: Taking into account comments above attributes for items

Fixes #14555
Fixes #15684
Fixes #15754

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github-actions bot commented Sep 24, 2025 •
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Lintcheck changes for 5bd8cff

Lint Added Removed Changed
clippy::undocumented_unsafe_blocks 0 18 1
clippy::unnecessary_safety_comment 16 0 269

This comment will be updated if you push new changes

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teofr commented Sep 24, 2025 •
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I checked all the removed/added lints and they all make sense to me

  • All of the removed undocumented_unsafe_block are correct, and shouldn'te have been there in the first place
  • Most of the added unnecesary_safety_comment are because a // SAFETY: comment is used in an unsafe fn. Maybe we should improve the lint message in these cases to suggest a // # Safety comment instead
  • One is a SAFETY comment on a struct, which I think is correctly linted
  • One is a bug that's been uncovered by this PR but was present already (unnecessary_safety_comment and undocumented_unsafe_blocks visit the same comment twice #15755)
  • The changes are a bit strange, basically some notes regarding why the lint is enabled are deleted or added, does anyone know what could cause this?

@teofr teofr marked this pull request as ready for review September 24, 2025 15:14
@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties label Sep 24, 2025
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rustbot commented Sep 24, 2025

r? @samueltardieu

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@teofr teofr changed the title [unnecessary_safety_comment] Considering comments above attributes for items [unnecessary_safety_comment] Some fixes regarding comments above attributes Sep 26, 2025
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blyxyas commented Oct 2, 2025

r? blyxyas

Being that this is R4L-oriented, I'll give it priority

@rustbot rustbot assigned blyxyas and unassigned samueltardieu Oct 2, 2025
@blyxyas blyxyas added the G-Rust-for-Linux Issues related to Rust-for-Linux wants and bugfixes label Oct 2, 2025
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blyxyas commented Oct 2, 2025

Maybe we should improve the lint message in these cases to suggest a // # Safety comment instead

We totally should! could you add that case? (It should be simple)

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Great patch, but I have one request.
It's a bit hard to distinguish why you're being prompted to remove a SAFETY comment from an unsafe function without extra help. What about not linting when that SAFETY comment comes from a doc-comment, as it will be rendered as useful information for consumers?

Also, if it's not a doc-comment, we can suggest to make it into a doc comment (/// # Safety)

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clippy_lints/src/undocumented_unsafe_blocks.rs
Some((start + (text.len() - trimmed.len()), trimmed))
})
.filter(|(_, text)| !text.is_empty());
.filter(|(_, text)| !(text.is_empty() || (accept_comment_above_attributes && is_attribute(text))));
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I really like how you managed to do a solution so elegant.

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Thanks! I really appreciate it

@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action from the author. (Use `@rustbot ready` to update this status) and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties labels Oct 3, 2025
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@teofr teofr force-pushed the issue-14555 branch 2 times, most recently from 90eee6e to 05d5c5d Compare October 5, 2025 11:59
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teofr commented Oct 5, 2025

Hey, thanks for the review!

I tried to reach a (useful) middle grounds, if there's a SAFETY: comment over an unsafe function:

  • if it's a doc comment, I try to suggest the change (not very smart at the moment)
  • if it's a regular comment, I provide help indicating than a # Safety doc comment section could be better

I modified what position is used for the lint, so I don't need to find the position of SAFETY, which changes a lot (269) of lints. If this is discouraged or not worth for this fix I can bring back the original span, and just handle the suggestion cases by hand.

Anyways, I think this lint deserves a bigger refactor (I'd like to work on it, but have no time right now). #15755 and #clippy > broken lint: `undocumented_unsafe_blocks`

Let me know what you think

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@rustbot 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 from the author. (Use `@rustbot ready` to update this status) labels Oct 5, 2025
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rustbot commented Oct 7, 2025

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.

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