error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
  --> $DIR/issue-111554.rs:5:16
   |
LL |         || bar(&mut self);
   |                ^^^^^^^^^ cannot borrow as mutable

error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
  --> $DIR/issue-111554.rs:10:16
   |
LL |         || bar(&mut self);
   |                ^^^^^^^^^ cannot borrow as mutable

error[E0596]: cannot borrow data in a `&` reference as mutable
  --> $DIR/issue-111554.rs:10:16
   |
LL |         || bar(&mut self);
   |                ^^^^^^^^^ cannot borrow as mutable

error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
  --> $DIR/issue-111554.rs:21:16
   |
LL |         || bar(&mut self);
   |                ^^^^^^^^^ cannot borrow as mutable
   |
help: consider changing this to be mutable
   |
LL |     pub fn quux(mut self) {
   |                 +++

error: aborting due to 4 previous errors

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