FP redundant_pattern lifetime mismatch

[matthiaskrgr]

Summary

.

Lint Name

redundant_pattern

Reproducer

I tried this code:

#![warn(clippy::redundant_pattern)]
fn _f(mut p @ _: &mut i32) {
    let mut number = 111;
    p = &mut number;
    *p = 2;
    println!("{}", *p);
}

pub fn main() {}

I saw this happen:

warning: the `p @ _` pattern can be written as just `p`
 --> src/main.rs:2:7
  |
2 | fn _f(mut p @ _: &mut i32) {
  |       ^^^^^^^^^ help: try: `mut p`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_pattern
note: the lint level is defined here
 --> src/main.rs:1:9
  |
1 | #![warn(clippy::redundant_pattern)]
  |         ^^^^^^^^^^^^^^^^^^^^^^^^^

the suggested code

#![warn(clippy::redundant_pattern)]
fn _f(mut p: &mut i32) {
    let mut number = 111;
    p = &mut number;
    *p = 2;
    println!("{}", *p);
}

pub fn main() {}

does not compile:

warning: value passed to `p` is never read
 --> src/main.rs:2:11
  |
2 | fn _f(mut p: &mut i32) {
  |           ^
  |
  = help: maybe it is overwritten before being read?
  = note: `#[warn(unused_assignments)]` on by default

error[E0597]: `number` does not live long enough
 --> src/main.rs:4:9
  |
2 | fn _f(mut p: &mut i32) {
  |              - let's call the lifetime of this reference `'1`
3 |     let mut number = 111;
  |         ---------- binding `number` declared here
4 |     p = &mut number;
  |     ----^^^^^^^^^^^
  |     |   |
  |     |   borrowed value does not live long enough
  |     assignment requires that `number` is borrowed for `'1`
...
7 | }
  | - `number` dropped here while still borrowed

For more information about this error, try `rustc --explain E0597`.

Version

Additional Labels

No response

[matthiaskrgr]

rustc 1.89.0-nightly (1bbd62e54 2025-05-29)
binary: rustc
commit-hash: 1bbd62e547ba5cc08ccb44c27def3d33195d2dd5
commit-date: 2025-05-29
host: x86_64-unknown-linux-gnu
release: 1.89.0-nightly
LLVM version: 20.1.5