warning: unreachable pattern
  --> $DIR/packed_pattern2.rs:24:9
   |
LL |         Bar { a: Foo { field: (5, 6) } } => {},
   |         -------------------------------- matches all the relevant values
LL |         FOO => unreachable!(),
   |         ^^^ no value can reach this
   |
   = note: `#[warn(unreachable_patterns)]` on by default

warning: 1 warning emitted