小编taR*_*sty的帖子

我正在从https://rust-cli.github.io/book/tutorial/testing.html学习 rust cli 教程，但遇到了编译器警告：

unused `std::result::Result` that must be used
  --> src/main.rs:15:13
   |
15 |             writeln!(writer, "{}", line);

这是完整的代码：

use exitfailure::ExitFailure;
use failure::ResultExt;
use structopt::StructOpt;

#[derive(StructOpt)]
struct Cli {
    pattern: String,
    #[structopt(parse(from_os_str))]
    path: std::path::PathBuf,
}

fn find_matches(content: &str, pattern: &str, mut writer: impl std::io::Write) {
    for line in content.lines() {
        if line.contains(pattern) {
            writeln!(writer, "{}", line);
        }
    }
}

#[test]
fn find_a_match() {
    let mut result = Vec::new();
    find_matches("lorem ipsum\ndolor sit amet", "lorem", &mut result);
    assert_eq!(result, b"lorem ipsum\n"); …