相关疑难解决方法(0)

为什么这段代码不能编译？

use std::{fs, path::Path};

fn main() {
    let dir = Path::new("../FileSystem");

    if !dir.is_dir() {
        println!("Is not a directory");
        return;
    }

    for item in try!(fs::read_dir(dir)) {
        let file = match item {
            Err(e) => {
                println!("Error: {}", e);
                return;
            }
            Ok(f) => f,
        };

        println!("");
    }

    println!("Done");
}

这是我得到的错误

error[E0308]: mismatched types
  --> src/main.rs:11:17
   |
11 |     for item in try!(fs::read_dir(dir)) {
   |                 ^^^^^^^^^^^^^^^^^^^^^^^ expected (), found enum `std::result::Result`
   |
   = note: expected type `()`
              found type `std::result::Result<_, _>`
   = note: …

我写了一个基于Rust文档的非常简单的脚本:

use std::fs::{self, DirEntry};
use std::path::Path;

fn main() {
    let path = Path::new(".");
    for entry in fs::read_dir(path)? {
        let entry = entry?;
        let path = entry.path();
        if path.is_dir() {
            println!("directory found!");
        }
    }

}

但我得到以下编译错误?:

error[E0277]: the trait bound `(): std::ops::Carrier` is not satisfied
 --> test.rs:6:18
  |
6 |     for entry in fs::read_dir(path)? {
  |                  -------------------
  |                  |
  |                  the trait `std::ops::Carrier` is not implemented for `()`
  |                  in this macro invocation
  |
  = note: required …