`cargo clippy --fix` don't remove redundant `mut`

[MCJOHN974]

Summary

cargo clippy --fix can autofix more problems

Reproducer

I tried this code:

fn foo(_x: &i32) {}

fn main() {
    let mut x = 5i32;
    foo(&mut x);         // this mut is redundant
}

I expected to see this happen:

cargo clippy --fix removes this redundant mut.

Instead, this happened:

cargo clippy --fix warns about this redundant mut

I don't see any use cases were this mut can make side effects and it is not safe to remove it automatically. Is it just not implemented yet or there are some cases where auto removing this mut can bring side effects?

Version

rustc 1.85.0-nightly (21fe748be 2024-12-11)
binary: rustc
commit-hash: 21fe748be15271ea5804e0507cd699b675efe038
commit-date: 2024-12-11
host: aarch64-apple-darwin
release: 1.85.0-nightly
LLVM version: 19.1.5

Additional Labels

No response

Summary Notes

• "Best claimed by first-timers" by @samueltardieu

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[samueltardieu]

This is not a bug, but an enhancement request. You are right, this could be suggested by Clippy, and auto-applied in most (all?) cases.

@rustbot label -C-bug +C-enhancement +good-first-issue

[rustbot]

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[MCJOHN974]

Thanks @samueltardieu for your answers! I'd like to try take this one, and since I'm newcomer it may take a time for me, so will appreciate if more experienced contributors won't take this for a while

[MCJOHN974]

@rustbot claim

[samueltardieu]

Note for our regular contributors: please keep issues labelled "good-first-issue" for people wanting to dip their toes into Clippy's code with something easy. Feel free to claim them if they haven't found someone in months though.

(I know this is claimed already, I'm testing the note feature)

@rustbot note "Best claimed by first-timers"

[ada4a]

This is duplicate of #8943, which I fixed in #15438 because I hadn't seen this issue and thus didn't know it was supposed to be left to first-time contributors -- sorry about that^^

@rustbot label S-fixed