Add clippy::cast_possible_wrap to the lint set#135
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tomcur merged 1 commit intolinebender:mainfrom Jan 16, 2026
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`clippy::cast_possible_wrap` checks for casting an unsigned integer to a signed integer of the same size. If the value is too large to fit in the signed integer, it will wrap around to negative numbers. Such casts will usually be used when doing some math, so scrutiny of the cast is probably welcome. It's similar to the already-enabled `clippy::cast_possible_truncation`. See linebender/vello#1364 for an example where the lint is useful. The similar lint `clippy::cast_sign_loss` more or less does the opposite, triggering for casts from signed to unsigned numeric types. Floats are included in this lint, as they do a saturating cast, making it more likely to have false positives: it triggers 65 times on `vello_common` currently. Perhaps this one should not be added to the canonical lint set.
DJMcNab
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The important reason for my approval here is that uN::cast_signed are now a more idiomatic way to represent the cases where these semantics are desired.
xStrom
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In theory this should detect cases that require extra attention, so it's fine.
The classic Clippy fear is there, that it will be super noisy. However, I ran this against the Xilem repo and didn't get a single hit, Kurbo only got two hits. So perhaps it's not too noisy after all. Let's try it out!
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See also rust-lang/rust-clippy#16407 |
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Fixed by adding a reasonable limitation on `MAX_KERNEL_SIZE`, and storing the kernel size as a `u8` instead of `usize`. The lint itself checks for possible wrapping when going from an unsigned to signed integer, and is not currently in our lint set (hence not triggered on CI). It triggers when manually requested. It probably should be included in the lint set, but that's for another time (linebender/linebender.github.io#135).
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clippy::cast_possible_wrapchecks for casting an unsigned integer to a signed integer of the same size. If the value is too large to fit in the signed integer, it will wrap around to negative numbers. Such casts will usually be used when doing some math, so scrutiny of the cast is probably welcome. It's similar to the already-enabledclippy::cast_possible_truncation.See linebender/vello#1364 for an example where the lint is useful.
The similar lint
clippy::cast_sign_lossmore or less does the opposite, triggering for casts from signed to unsigned numeric types. Floats are included in this lint, as they do a saturating cast, making it more likely to have false positives: it triggers 65 times onvello_commoncurrently. Perhaps this one should not be added to the canonical lint set (and I have not proposed adding it here).For the interested reader, rust-lang/rust-clippy#9231 has some further discussion of these lints.