rust - 不能取消引用 `std::result::Result`类型

Question

use std::env;
use std::fs::File;
use std::io::{BufReader, BufWriter, Read, Write};

fn main() {
    let args = env::args().collect::<Vec<String>>();
    let file = File::open(&args[1]).expect("file not found");
    let reader = BufReader::new(file);
    let mut writer = BufWriter::new(std::io::stdout());
    for it in reader.bytes() {
        writer.write(&[*it]);
    }
}

为什么这会产生错误？

type `std::result::Result<u8, std::io::Error>` cannot be dereferenced

Answer 1

从documentation，

fn bytes(self) -> Bytes<Self> where
    Self: Sized, 

Transforms this Read instance to an Iterator over its bytes.

The returned type implements Iterator where the Item is Result<u8,io::Error>. The yielded item is Ok if a byte was successfully read andErr otherwise. EOF is mapped to returning None from this iterator.

只能取消实现 std::ops::Deref的类型。

use std::env;
use std::fs::File;
use std::io::{BufReader, BufWriter, Read, Write};

fn main() {
    let args = env::args().collect::<Vec<String>>();
    let file = File::open(&args[1]).expect("file not found");
    let reader = BufReader::new(file);
    let mut writer = BufWriter::new(std::io::stdout());
    for it in reader.bytes() {
        writer.write(&[it.unwrap()]);
    }
}