ices/105321.rs: fixed with errors

[github-actions]

Issue: rust-lang/rust#105321

fn hof<F>(_: F)
where
    F: FnMut() -> (),
{
}

fn f() -> _ {
    hof(f);
}

fn main() {}

=== stdout ===
=== stderr ===
error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
 --> /home/runner/work/glacier/glacier/ices/105321.rs:7:11
  |
7 | fn f() -> _ {
  |           ^
  |           |
  |           not allowed in type signatures
  |           help: replace with the correct return type: `()`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0121`.
==============