What I am trying to do

我有从std::str::SplitWhitespace返回的in迭代器，我需要第一个元素，以及所有元素的一个向量.

What I have tried

我试着用偷窥.然而，这似乎需要一个可变的(我不能我们为什么)，我以borrow 错误结束.

Simplified code, with compile errors.

fn main(){
    let line = "hello, world";
    let mut tokens = line.split_whitespace().peekable();
    if let Some(first) = tokens.peek() {
        //println!("{first}"); //works
        //println!("{tokens:?}"); // works
        println!("{first}\n{tokens:?}"); //compile error
    }
}

error[E0502]: cannot borrow `tokens` as immutable because it is also borrowed as mutable
 --> src/main.rs:7:29
  |
4 |     if let Some(first) = tokens.peek() {
  |                          ------------- mutable borrow occurs here
...
7 |         println!("{first}\n{tokens:?}"); //error
  |         --------------------^^^^^^-----
  |         |                   |
  |         |                   immutable borrow occurs here
  |         mutable borrow later used here

如果我不 comments 这两个println，而 comments 错误的那个.那它就起作用了.这导致我添加了一个克隆let first = first.clone();，在println之前.这解决了它，但我想知道是否有更好的方法.