// This is not exactly right, yet. // Ideally we should be suggesting `as_mut` for the first case, // and suggesting to change `as_ref` to `as_mut` in the second. fn x(cb: &mut Option<&mut dyn FnMut()>) { cb.map(|cb| cb()); //~^ ERROR cannot move out of `*cb` which is behind a mutable reference } fn x2(cb: &mut Option<&mut dyn FnMut()>) { cb.as_ref().map(|cb| cb()); //~^ ERROR cannot borrow `*cb` as mutable, as it is behind a `&` reference } fn main() {}