error[E0525]: expected a closure that implements the `AsyncFn` trait, but this closure only implements `AsyncFnMut`
  --> $DIR/kind-due-to-arg-with-box-wrap.rs:13:32
   |
LL |         takes_asyncfn(Box::new(async || self.an_async_fn().await));
   |         ------------- ---------^^^^^^^^--------------------------
   |         |             |        |        |
   |         |             |        |        closure is `AsyncFnMut` because it mutates the variable `*self` here
   |         |             |        this closure implements `AsyncFnMut`, not `AsyncFn`
   |         |             the requirement to implement `AsyncFn` derives from here
   |         required by a bound introduced by this call
   |
   = note: required for `Box<{async closure@$DIR/kind-due-to-arg-with-box-wrap.rs:13:32: 13:40}>` to implement `AsyncFn()`
note: required by a bound in `takes_asyncfn`
  --> $DIR/kind-due-to-arg-with-box-wrap.rs:18:32
   |
LL | async fn takes_asyncfn(_: impl AsyncFn()) {
   |                                ^^^^^^^^^ required by this bound in `takes_asyncfn`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0525`.