1 error[E0525]: expected a closure that implements the `Fn` trait, but this closure only implements `FnMut`
2 --> $DIR/issue-26046-fn-mut.rs:4:19
4 LL | let closure = || {
5 | ^^ this closure implements `FnMut`, not `Fn`
7 | --- closure is `FnMut` because it mutates the variable `num` here
10 | ----------------- the requirement to implement `Fn` derives from here
12 = note: required for the cast from `[closure@$DIR/issue-26046-fn-mut.rs:4:19: 4:21]` to the object type `dyn Fn()`
14 error: aborting due to previous error
16 For more information about this error, try `rustc --explain E0525`.