warning: unused coroutine that must be used
  --> $DIR/reborrow-mut-upvar.rs:6:5
   |
LL | /     || {
LL | |         {
LL | |             let _baz = &*bar;
LL | |             yield;
...  |
LL | |         *bar = 2;
LL | |     };
   | |_____^
   |
   = note: coroutines are lazy and do nothing unless resumed
   = note: `#[warn(unused_must_use)]` on by default

warning: 1 warning emitted