| error[E0525]: expected a closure that implements the `Fn` trait, but this closure only implements `FnMut` |
| --> $DIR/issue-26046-fn-mut.rs:14:19 |
| | |
| LL | let closure = || { //~ ERROR expected a closure that |
| | ^^ this closure implements `FnMut`, not `Fn` |
| LL | num += 1; |
| | --- closure is `FnMut` because it mutates the variable `num` here |
| ... |
| LL | Box::new(closure) |
| | ----------------- the requirement to implement `Fn` derives from here |
| |
| error: aborting due to previous error |
| |
| For more information about this error, try `rustc --explain E0525`. |