error: field is never read: `b`
  --> $DIR/union-lint-dead-code.rs:8:5
   |
LL |     b: bool,
   |     ^^^^^^^
   |
note: the lint level is defined here
  --> $DIR/union-lint-dead-code.rs:4:9
   |
LL | #![deny(dead_code)]
   |         ^^^^^^^^^

error: aborting due to previous error