unit_arg breaks code

Summary

.

Lint Name

unit_arg

Reproducer

I tried this code:

#![allow(dead_code)]
#![allow(unused_assignments)]
#![allow(unused_variables)]
#![allow(unreachable_code)]

trait UnitDefault {
    fn default() -> Self;
}

impl UnitDefault for () {
    fn default() -> () {
        panic!()
    }
}

fn match_arm() {
    let _x = match Ok(UnitDefault::default()) {
        Ok(v) => v,
        Err(()) => return,
    };
}

fn match_arm_rev() {
    let _x = match Ok(UnitDefault::default()) {
        Err(()) => return,
        Ok(v) => v,
    };
}

fn main() {}

I saw this happen:

after fixes were automatically applied the compiler reported errors within these files:

  * src/main.rs

This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag

The following errors were reported:
error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
  --> src/main.rs:18:9
   |
7  |     fn default() -> Self;
   |     --------------------- `UnitDefault::default` defined here
...
18 |         UnitDefault::default();
   |         ^^^^^^^^^^^^^^^^^^^^ cannot call associated function of trait

error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
  --> src/main.rs:28:9
   |
7  |     fn default() -> Self;
   |     --------------------- `UnitDefault::default` defined here
...
28 |         UnitDefault::default();
   |         ^^^^^^^^^^^^^^^^^^^^ cannot call associated function of trait

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0790`.
Original diagnostics will follow.

warning: passing a unit value to a function
  --> src/main.rs:17:20
   |
17 |     let _x = match Ok(UnitDefault::default()) {
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unit_arg
   = note: requested on the command line with `-W clippy::unit-arg`
help: move the expression in front of the call and replace it with the unit literal `()`
   |
17 ~     let _x = match {
18 +         UnitDefault::default();
19 +         Ok(())
20 ~     } {
   |

warning: passing a unit value to a function
  --> src/main.rs:24:20
   |
24 |     let _x = match Ok(UnitDefault::default()) {
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unit_arg
help: move the expression in front of the call and replace it with the unit literal `()`
   |
24 ~     let _x = match {
25 +         UnitDefault::default();
26 +         Ok(())
27 ~     } {
   |

Version

rustc 1.67.0-nightly (c97b539e4 2022-11-30)
binary: rustc
commit-hash: c97b539e408ea353f4fde2f9251d598291fec421
commit-date: 2022-11-30
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4

Additional Labels

No response

Reproduce the unit_arg lint issue using the Rust code in the report and observe the compiler errors in src/main.rs after automatic fixes are applied. Inspect the unit_arg lint's suggestion behavior; done when applying its suggestion no longer produces E0790 errors.