error[E0596]: cannot borrow data in a `&` reference as mutable
  --> $DIR/let-else-binding-explicit-mut-borrow.rs:7:37
   |
LL |     let Some(n): &mut Option<i32> = &mut &Some(5i32) else {
   |                                     ^^^^^^^^^^^^^^^^ cannot borrow as mutable

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0596`.