Restrict unnecessary_sort_by to non-reference, Copy types #6006
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Restrict unnecessary_sort_by to non-reference, Copy types `Vec::sort_by_key` closure parameter is `F: FnMut(&T) -> K`. The lint's suggestion destructures the `T` parameter; this was probably done to avoid different unnamed lifetimes when `K = Reverse<&T>`. This change fixes two issues: * Destructuring T when T is non-reference requires the type to be Copy, otherwise we would try to move from a shared reference. We make sure `T: Copy` holds. * Make sure `T` is actually non-reference. I didn't go for destructuring multiple levels of references, as we would have to compensate in the closure body by removing derefs and maybe adding parens, which would add more complexity. changelog: Restrict [`unnecessary_sort_by`] to non-reference, Copy types Fixes #6001
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@bors r=Manishearth |
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📌 Commit 9fa9208 has been approved by |
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☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test |
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unnecessary sort by: avoid dereferencing the suggested closure parameter This change tries to simplify the solution for problematic cases but is less restrictive than #6006. * We can't dereference shared references to non-Copy types, so the new suggestion does not do that. Note that this implies that the suggested closure parameter will be a reference. * We can't take a reference to the closure parameter in the returned key, so we don't lint in those cases. This can happen either because the key borrows from the parameter (e.g. `|a| a.borrows()`), or because we suggest `|a| Reverse(a)`. If we did we would hit this error: ``` error: lifetime may not live long enough --> /home/ebroto/src/ebroto-clippy/tests/ui/unnecessary_sort_by.fixed:19:25 | 19 | vec.sort_by_key(|b| Reverse(b)); | -- ^^^^^^^^^^ returning this value requires that `'1` must outlive `'2` | || | |return type of closure is Reverse<&'2 isize> | has type `&'1 isize` error: aborting due to previous error ``` Note that Clippy does not currently have the (MIR-based) machinery necessary to check that what is borrowed is actually the closure parameter. changelog: [`unnecessary_sort_by`]: avoid dereferencing the suggested closure parameter Fixes #6001
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Vec::sort_by_keyclosure parameter isF: FnMut(&T) -> K. The lint's suggestion destructures theTparameter; this was probably done to avoid different unnamed lifetimes whenK = Reverse<&T>.This change fixes two issues:
T: Copyholds.Tis actually non-reference. I didn't go for destructuring multiple levels of references, as we would have to compensate in the closure body by removing derefs and maybe adding parens, which would add more complexity.changelog: Restrict [
unnecessary_sort_by] to non-reference, Copy typesFixes #6001