error[E0525]: expected a closure that implements the `Fn` trait, but this closure only implements `FnMut` | |
--> $DIR/issue-26046-fn-mut.rs:4:19 | |
| | |
LL | let closure = || { | |
| ^^ 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`. |