struct Config {
    query: String,
    filename: String,
}

fn main() {
    let args: Vec<String> = env::args().collect();
    let config = Config::new(&args)
}

impl Config {
    fn new(args: &[String]) -> Result<Config, &'static str> {
        // [...]
        let query = args[1].clone();
        let filename = args[2].clone();
        // [...]
    }
}

fn main() {
    let config = Config::new(env::args())
}

impl Config {
    fn new(mut args: std::env::Args) -> Result<Config, &'static str> {
        args.next();

        let query = match args.next() {
            Some(arg) => arg,
            None => return Err("Didn't get a query string"),
        };

        let filename = match args.next() {
            Some(arg) => arg,
            None => return Err("Didn't get a file name"),
        };
        // [...]
    }
}