error: field `b` is never read
  --> $DIR/union-lint-dead-code.rs:8:5
   |
LL | union Foo {
   |       --- field in this union
LL |     x: usize,
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 1 previous error