error[E0599]: no method named `set_unused_1` found for struct `Sparse` in the current scope
  --> $DIR/use-skipped-setter-2.rs:13:12
   |
4  | / #[derive(Debug)]
5  | | pub struct Sparse {
   | |___- method `set_unused_1` not found for this
...
13 |       sparse.set_unused_1(0); // ERROR!
   |              ^^^^^^^^^^^^ method not found in `Sparse`