`ignored-unit-patterns` ignores mutability

[matthiaskrgr]

EDIT

Using the following flags

--force-warn clippy::ignored-unit-patterns

this code:

//@ edition:2021
//@ check-pass
#![feature(coroutines, stmt_expr_attributes)]

fn main() {
    let x = &mut ();
    || {
        let _c = #[coroutine]
        || yield *&mut *x;
        || _ = &mut *x;
    };
}

caused the following diagnostics:

    Checking _issue-110929-coroutine-conflict-error-ice v0.1.0 (/tmp/icemaker_global_tempdir.EuHmIYit9wj1/icemaker_clippyfix_tempdir.wfNVWxul8RLV/_issue-110929-coroutine-conflict-error-ice)
warning: matching over `()` is more explicit
  --> src/main.rs:10:12
   |
10 |         || _ = &mut *x;
   |            ^ help: use `()` instead of `_`: `()`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ignored_unit_patterns
   = note: requested on the command line with `--force-warn clippy::ignored-unit-patterns`

warning: `_issue-110929-coroutine-conflict-error-ice` (bin "_issue-110929-coroutine-conflict-error-ice") generated 1 warning (run `cargo clippy --fix --bin "_issue-110929-coroutine-conflict-error-ice"` to apply 1 suggestion)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.11s

However after applying these diagnostics, the resulting code:

//@ edition:2021
//@ check-pass
#![feature(coroutines, stmt_expr_attributes)]

fn main() {
    let x = &mut ();
    || {
        let _c = #[coroutine]
        || yield *&mut *x;
        || () = &mut *x;
    };
}

no longer compiled:

    Checking _issue-110929-coroutine-conflict-error-ice v0.1.0 (/tmp/icemaker_global_tempdir.EuHmIYit9wj1/icemaker_clippyfix_tempdir.wfNVWxul8RLV/_issue-110929-coroutine-conflict-error-ice)
error[E0308]: mismatched types
  --> src/main.rs:10:12
   |
10 |         || () = &mut *x;
   |            ^^   ------- this expression has type `&mut ()`
   |            |
   |            expected `&mut ()`, found `()`

For more information about this error, try `rustc --explain E0308`.
error: could not compile `_issue-110929-coroutine-conflict-error-ice` (bin "_issue-110929-coroutine-conflict-error-ice") due to 1 previous error
warning: build failed, waiting for other jobs to finish...
error: could not compile `_issue-110929-coroutine-conflict-error-ice` (bin "_issue-110929-coroutine-conflict-error-ice" test) due to 1 previous error

Version:

rustc 1.90.0-nightly (5e749eb66 2025-06-29)
binary: rustc
commit-hash: 5e749eb66f93ee998145399fbdde337e57cd72ef
commit-date: 2025-06-29
host: x86_64-unknown-linux-gnu
release: 1.90.0-nightly
LLVM version: 20.1.7