struct Service {
    is_admin: bool,
    is_authed: bool,
    is_logged_out: bool,
}

impl Service {

    fn authenticate<S>(&mut self, passwd: S) -> Result<(), String>
        where S: AsRef<str>
    {
        if passwd.as_ref() == "secretpassword" {
            self.is_authed = true;
            Ok(())
        } else {
            Err("Bad password".into())
        }
    }

    fn escalate<S>(&mut self, passwd: S) -> Result<(), String>
            where S: AsRef<str>
    {
        if passwd.as_ref() == "adminpasswd" {
            self.is_admin = true;
            Ok(())
        } else {
            Err("Bad password".into())
        }
    }

    fn perform_action(&self) {
        assert!(self.is_authed)
        println!("we are authed")
    }

    fn perform_admin_action(&self) {
        assert!(self.is_admin)
        println!("we are admin")
    }

}