error: variant `Bar` is never constructed
  --> $DIR/unused-struct-variant.rs:8:5
   |
LL | enum E {
   |      - variant in this enum
LL |     Foo(F),
LL |     Bar(B),
   |     ^^^
   |
note: the lint level is defined here
  --> $DIR/unused-struct-variant.rs:1:9
   |
LL | #![deny(unused)]
   |         ^^^^^^
   = note: `#[deny(dead_code)]` implied by `#[deny(unused)]`

error: aborting due to 1 previous error