fn main() {
    let strings = vec![String::from("hello")];
    let default = String::from("default");
    let s = first_or(&strings, &default);
    println!("{}", s);
}

fn first_or(strings: &Vec<String>, default: &String) -> &String {
    if strings.len() > 0 {
        &strings[0]
    } else {
        default
    }
}

I tried to just either return &string[0] or default, but the error persisted. I dont want how to solve this error, but what specific part of this code is causing it and why?