error[E0499]: cannot borrow `*heap` as mutable more than once at a time
  --> $DIR/issue-85581.rs:9:22
   |
LL |     match heap.peek_mut() {
   |           ---------------
   |           |
   |           first mutable borrow occurs here
   |           a temporary with access to the first borrow is created here ...
LL |         Some(_) => { heap.pop(); },
   |                      ^^^^ second mutable borrow occurs here
...
LL | }
   | - ... and the first borrow might be used here, when that temporary is dropped and runs the destructor for type `Option<PeekMut<'_, i32>>`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0499`.