error: Must declare the overseer error type via `error=..`.
  --> $DIR/err-04-missing-error.rs:16:1
   |
16 | #[overlord(signal=SigSigSig, event=Event, gen=AllMessages)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in the attribute macro `overlord` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0433]: failed to resolve: use of undeclared type `Overseer`
  --> $DIR/err-04-missing-error.rs:30:10
   |
30 |     let _ = Overseer::builder()
   |             ^^^^^^^^ use of undeclared type `Overseer`