warning: method `dummy` is never used
  --> $DIR/enum-null-pointer-opt.rs:10:18
   |
LL | trait Trait { fn dummy(&self) { } }
   |       -----      ^^^^^
   |       |
   |       method in this trait
   |
   = note: `#[warn(dead_code)]` on by default

warning: 1 warning emitted