error: struct `F` is never constructed
  --> $DIR/unused-enum.rs:3:8
   |
LL | struct F;
   |        ^
   |
note: the lint level is defined here
  --> $DIR/unused-enum.rs:1:9
   |
LL | #![deny(unused)]
   |         ^^^^^^
   = note: `#[deny(dead_code)]` implied by `#[deny(unused)]`

error: struct `B` is never constructed
  --> $DIR/unused-enum.rs:4:8
   |
LL | struct B;
   |        ^

error: enum `E` is never used
  --> $DIR/unused-enum.rs:6:6
   |
LL | enum E {
   |      ^

error: aborting due to 3 previous errors