error[E0597]: `db` does not live long enough
 --> $DIR/checkpoint_outlive_db.rs:6:25
  |
4 |     let _checkpoint = {
  |         ----------- borrow later stored here
5 |         let db = DB::open_default("foo").unwrap();
6 |         Checkpoint::new(&db)
  |                         ^^^ borrowed value does not live long enough
7 |     };
  |     - `db` dropped here while still borrowed