我是一个新手。我被下面的代码卡住了。

let mut all_iterators: Vec<Chars> = Vec::new();
    for s in strings {
        let a = s.chars();
        all_iterators.push(a);
    }

    let common_str: &str = "";
    loop {
        let common_char: Option<char>;

        for s in &all_iterators {
            if let Some(temp) = (*s).next() {}
        }
    }

在(*s).next()上出现以下错误

cannot borrow `*s` as mutable, as it is behind a `&` reference
`s` is a `&` reference, so the data it refers to cannot be borrowed as mutable

任何帮助都将不胜感激。你能解释一下我在哪里出了问题吗？