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Add the iter_last_slice lint #15496

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Add the iter_last_slice lint #15496

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@scrabsha scrabsha commented Aug 15, 2025 •
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Fixes #15487.

This lint triggers when calling .iter().last() on a slice or array and suggests using .last() directly.

This is a modified version of the iter_next_slice. I could not figure out how to avoid code duplication though :/.

changelog: Add iter_last_slice lint

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rustbot commented Aug 15, 2025

r? @y21

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@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties label Aug 15, 2025
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github-actions bot commented Aug 15, 2025 •
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No changes for 8ea1451

@rustbot rustbot added S-blocked Status: marked as blocked ❌ on something else such as an RFC or other implementation work A-lint Area: New lints and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties labels Aug 15, 2025
@scrabsha
Add the iter_last_slice lint
8ea1451 
This lint triggers when calling `.iter().last()` on a slice or array
and suggests using `.last()` directly.

This is a modified version of the `iter_next_slice`. I could not figure
out how to avoid code duplication though :/.
ada4a
ada4a reviewed Aug 15, 2025
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some drive-by comments..

clippy_lints/src/methods/mod.rs
iter_overeager_cloned::Op::LaterCloned,
false,
);
double_ended_iterator_last::check(cx, expr, recv, call_span);
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Why repeat this check in two match arms? I think leaving it outside the match is fine..

tests/ui/iter_last_slice.rs

let _ = s.iter().last();
//~^ iter_last_slice
// Should be replaced by s.last()
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I think these comments could be left out -- the .fixed file already captures the intended output

clippy_lints/src/methods/iter_last_slice.rs
cx,
ITER_LAST_SLICE,
expr.span,
"using `.iter().last()` on a slice without end index",
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Suggested change
"using `.iter().last()` on a slice without end index",
"using `.iter().last()` on a slice without start index",

@samueltardieu samueltardieu added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties and removed S-blocked Status: marked as blocked ❌ on something else such as an RFC or other implementation work labels Sep 17, 2025
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rustbot commented Oct 11, 2025

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

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ada4a commented Oct 11, 2025 •
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@rustbot note remove Feature-freeze

@scrabsha friendly ping from triage, do you still plan to work on this?

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scrabsha commented Oct 11, 2025

@ada4a I don't have much energy to dedicate to this PR (and to open source in general) for health reasons. Things should go better in 2-3 weeks. If that's too long, you can close this PR and I will reopen a new one (with all the points you railed addressed) when I'm back :)

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ada4a commented Oct 11, 2025

I don't have much energy to dedicate to this PR (and to open source in general) for health reasons.

Sorry to hear that, wishing you a swift recovery!

Things should go better in 2-3 weeks. If that's too long, you can close this PR

No need, it can wait for a bit:)

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Lint against [T].iter().last() and suggest [T].last()

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