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Add undocumented_as_casts lint#16682

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Add undocumented_as_casts lint#16682
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@charlieHsiuC charlieHsiuC commented Mar 7, 2026 •
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Checks for as casts that do not have a preceding // CAST: comment.

fixes #15963

changelog: new lint: [undocumented_as_casts]

@rustbot rustbot added needs-fcp PRs that add, remove, or rename lints and need an FCP S-waiting-on-review Status: Awaiting review from the assignee but also interested parties labels Mar 7, 2026
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rustbot commented Mar 7, 2026

r? @samueltardieu

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github-actions bot commented Mar 7, 2026 •
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Lintcheck changes for d3a2c82

Lint Added Removed Changed
clippy::undocumented_as_casts 8647 0 0

This comment will be updated if you push new changes

@ojeda ojeda mentioned this pull request Mar 7, 2026
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Initial review.

Also, please add tests where parts of the cast expression come from a declarative macro. For example, a cast!(expr, type) which expands to (expr) as type, or a copy!(expr as type).

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Comment thread clippy_lints/src/undocumented_as_casts.rs Outdated
Comment thread clippy_lints/src/undocumented_as_casts.rs Outdated
Comment thread clippy_lints/src/undocumented_as_casts.rs Outdated
}
}

/// Checks if there is a `// CAST:` or `/* CAST:` comment preceding the cast expression.
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Wouldn't it be better to share the logic with the "SAFETY" logic? It looks like a lot of duplicated functionalities.

@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 Mar 7, 2026
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rustbot commented Mar 7, 2026

Reminder, once the PR becomes ready for a review, use @rustbot ready.

@samueltardieu samueltardieu added the lint-nominated Create an FCP-thread on Zulip for this PR label Mar 7, 2026
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rustbot commented Mar 7, 2026

This lint has been nominated for inclusion.

A FCP topic has been created on Zulip.

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charlieHsiuC commented Mar 11, 2026

Hi, @samueltardieu
I've updated the code based on your suggestions.

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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 Mar 11, 2026
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@charlieHsiuC
Add undocumented_as_casts lint to enforce comments on as casts
e8993bc
@charlieHsiuC
Fix doctest fail on example code
b49a3f4
@charlieHsiuC
Share check marked comment logic with undocumented_unsafe_blocks, a…
d0bde0f 
…dd test case for declared macro
@charlieHsiuC
Update safety comment handling to use more descriptive variable names
c1f6aa3
@charlieHsiuC
Implement checks for undocumented as casts with configurable options
d3a2c82 
- Added new configuration options: `check-undocumented-as-any-cast`, `check-undocumented-as-const-ptr-cast`, and `check-undocumented-as-mut-ptr-cast` to enforce documentation comments for `as` casts.
- Updated the linting logic to check for `// CAST:` comments for `as` casts, including specific checks for mutable and constant pointer casts.
- Enhanced documentation in the lint configuration and changelog to reflect the new checks.
- Created comprehensive tests to validate the behavior of the new lint checks, including scenarios with and without comments.
- Removed outdated test files related to the previous undocumented casts implementation.
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rustbot commented Apr 12, 2026

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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charlieHsiuC commented Apr 12, 2026

To allow the existing projects to gradually adopt this lint, I have added configurations to enable checks for specific scenarios that users may be most concerned about.

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rustbot commented Apr 14, 2026

☔ The latest upstream changes (possibly #16850) made this pull request unmergeable. Please resolve the merge conflicts.

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// CAST: ... comment on as casts

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