我是rust的新手，我正在构建grep命令的实现来学习这门语言。我试图创建一个函数来以不区分大小写的方式匹配搜索查询，但我在处理for循环中str.lines()迭代器返回值的生命周期时遇到了麻烦。
这是一个包含我正在实现的函数的最小可重复示例：

use grep::{run, Config};
use std::{env::args, process};

pub struct Config {
    file_path: String,
    query: String,
}
fn main() {
    let contents: Config =Config {query: "Hello world!".to_owned(), file_path: "test".to_owned()};
    let matches = search_case_sensitive(&config, &contents);
    print_matches(&matches);
    Ok(config)
}

type Match<'a> = Vec<(&'a str, &'a str, &'a str)>;

// this function causes the compile error
// contents -> the full text content of the file i previously read
// config.query -> the string i'm searching for inside contents
fn search_case_insensitive<'a>(config: &Config, contents: &'a str) -> Match<'a> {
    let mut matches: Match<'a> = Vec::new();
    let query = config.query.to_lowercase();
    for line in contents.lines() {
        let indexes = line.to_lowercase().match_indices(&query);
        for (i, found) in indexes {
            let prev = &line[..i];
            let next = &line[i + found.len()..];
            matches.push((prev, found, next));
        }
    }
    matches
}

字符串
编译时会出现这个错误：

error[E0716]: temporary value dropped while borrowed
  --> src/lib.rs:34:23
   |
34 |         let indexes = line.to_lowercase().match_indices(&query);
   |                       ^^^^^^^^^^^^^^^^^^^                      - temporary value is freed at the end of this statement
   |                       |
   |                       creates a temporary value which is freed while still in use
35 |         for (i, found) in indexes {
   |                           ------- borrow later used here
   |
   = note: consider using a `let` binding to create a longer lived value

型
据我所知，line应该被绑定到'a的生存期，因为它是对contents的每个元素的引用，但这并没有发生，所以line不是借用的，而是移动的，i的生存期不足以在indexes中使用。
如何从contents中借用line并将其绑定到'a生存期？