无法重新借用变量,因为我无法将不可变局部变量借用为可变

Question

我是Rust的新手,在借用检查器方面遇到了困难.

consume_byte来自main工作的电话就好了.但是,如果我尝试consume_two_bytes在它们之间添加另一个函数(),它们就会崩溃.

以下代码将无法编译,因为它似乎reader变量in consume_two_bytes不可变且无法借用.

添加&mut函数签名只会更改编译器错误.

use std::io::Read;
use std::net::TcpListener;

fn consume_byte<R>(reader: R) where R: Read {
    let mut buffer = vec![];
    reader.take(1).read_to_end(&mut buffer).unwrap();
}

fn consume_two_bytes<R>(reader: R) where R: Read {
    consume_byte(&mut reader);
    consume_byte(&mut reader);
}

fn main() {
    let listener = TcpListener::bind("127.0.0.1:8080").unwrap();
    let (mut stream, _) = listener.accept().unwrap();

    consume_byte(&mut stream);
    consume_byte(&mut stream);

    consume_two_bytes(&mut stream);
}

Answer 1

reader必须是可变的consume_two_bytes:

fn consume_two_bytes<R>(mut reader: R) where R: Read { // note the mut
    consume_byte(&mut reader);
    consume_byte(&mut reader);
}