Ah ok. I don't write Rust either but maybe it'd look like:

  impl State<Running> {
    pub fn next(self, Trigger<Hibernate>) -> State<Hibernate> {
        State { _inner: Hibernate {} }
    }

    pub fn next(self, Trigger<Terminate>) -> State<Terminate> {
        State { _inner: Terminate {} }
    }
  }