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