1 error[E0599]: no method named `f` found for fn pointer `fn(&u8)` in the current scope
2 --> $DIR/issue-57362-1.rs:20:7
5 | ----------- this trait defines an item `f`
8 | ^ method not found in `fn(&u8)`
10 = note: `a` is a function, perhaps you wish to call it
11 = help: items from traits can only be used if the trait is implemented and in scope
13 error: aborting due to previous error
15 For more information about this error, try `rustc --explain E0599`.