error: field is never used: `b`
  --> $DIR/union-lint-dead-code.rs:5:5
   |
LL |     b: bool,
   |     ^^^^^^^
   |
note: lint level defined here
  --> $DIR/union-lint-dead-code.rs:1:9
   |
LL | #![deny(dead_code)]
   |         ^^^^^^^^^

error: aborting due to previous error