error[E0596]: cannot borrow immutable item `*r` as mutable
  --> $DIR/issue-27282-reborrow-ref-mut-in-guard.rs:26:24
   |
LL |         ref mut r if { (|| { let bar = &mut *r; **bar = false; })();
   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot borrow as mutable

error: aborting due to previous error

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