struct MyError {
    code  int
    state string
}

pub fn (e MyError) msg() string {
    return 'something went wrong'
}

pub fn (e MyError) code() int {
    return e.code
}

fn foo() ! {
    return MyError{}
}

fn test_interface_err_msg_print() {
    foo() or {
        if err is MyError {
            eprintln(err.msg())
            exit(err.code())
        } else {
            panic(err)
        }
    }
}