| error[E0525]: expected a closure that implements the `Fn` trait, but this closure only implements `FnMut` | |
| --> $DIR/issue-34349.rs:16:17 | |
| | | |
| LL | let diary = || { | |
| | ^^ this closure implements `FnMut`, not `Fn` | |
| LL | farewell.push_str("!!!"); | |
| | -------- closure is `FnMut` because it mutates the variable `farewell` here | |
| ... | |
| LL | apply(diary); | |
| | ----- the requirement to implement `Fn` derives from here | |
| error: aborting due to previous error | |
| For more information about this error, try `rustc --explain E0525`. |