error[E0506]: cannot assign to `self.container_field` because it is borrowed
  --> $DIR/issue-81365-9.rs:21:9
   |
LL |         let first = &Deref::deref(self).target_field;
   |                                   ---- borrow of `self.container_field` occurs here
LL |         self.container_field = true;
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to borrowed `self.container_field` occurs here
LL |         first;
   |         ----- borrow later used here

error: aborting due to previous error

For more information about this error, try `rustc --explain E0506`.