rustc suggest adding "ref" before trait in derive attribute about rust HOT 2 CLOSED

error[E0382]: borrow of partially moved value: `self`
  --> src/main.rs:30:25
   |
26 | #[derive(Builder)]
   |          ------- value partially moved here
...
30 |     #[builder(default = "self.calc_b()")]
   |                         ^^^^^^^^^^^^^^^ value borrowed here after partial move
   |
   = note: partial move occurs because value has type `V`, which does not implement the `Copy` trait

For more information about this error, try `rustc --explain E0382`.