State machine using enums in Rust

enum_statemachine.rs

#[derive(Debug)]
enum State {
    New(Option<String>),
    Running(String),
    Failure(Box<State>),
}

enum Event {
    Open(String),
    Run,
}

impl State {
    // State transition logically consumes the state and event types
    fn event(self, event: Event) -> Self {
       match (&self, event) {
            (State::New(_), Event::Open(s)) => State::New(Some(s)),
            (State::New(Some(s)), Event::Run) => State::Running(s.to_owned()),
            _ => State::Failure(Box::new(self))
       } 
    }
}

fn main() {
    let mut machine = State::New(None);
    let events = vec![
        Event::Open("foo".to_owned()), // new(none) -> new(some("foo"))
        Event::Open("bar".to_owned()), // new(some("foo")) -> new(some("bar"))
        Event::Run, // new(some("bar")) -> running
        Event::Run, // running -> failure
    ];
    
    for event in events {
       machine = machine.event(event);
       dbg!(&machine);
    }
}