为什么借用会阻止在数组访问中内联函数调用?[副本]

我正在用Rust编写一些代码,用于生成46445645564584的Collatz序列中的前500个数字。

use std::fmt::Debug;

//Calculate the first 500 numbers in the Collatz sequence of 46445645645564584

fn main() {
    let mut v = vec![46445645645564584];

    for _ in 0..500 {
        let last = v[v.len() - 1];
        v.push(next(last));
    }

    print_array(&v);
}

fn next(n: i64) -> i64 {
    if n % 2 == 0 {
        n / 2
    } else {
        3 * n + 1
    }
}

fn print_array<T: Debug>(v: &[T]) {
    for x in v {
        println!("{:?}", x);
    }
}

这是可行的,但我想内联变量 last :

for _ in 0..500 {
    v.push(next(v[v.len() - 1]));
}

在我看来,这不应该改变程序的语义,因为我只是内联了一个变量。但是,当我尝试编译此文件时,Rust编译器会出现以下错误:

error[E0502]: cannot borrow `v` as immutable because it is also borrowed as mutable
 --> src/main.rs:9:21
  |
9 |         v.push(next(v[v.len() - 1]));
  |         -           ^              - mutable borrow ends here
  |         |           |
  |         |           immutable borrow occurs here
  |         mutable borrow occurs here

error[E0502]: cannot borrow `v` as immutable because it is also borrowed as mutable
 --> src/main.rs:9:23
  |
9 |         v.push(next(v[v.len() - 1]));
  |         -             ^            - mutable borrow ends here
  |         |             |
  |         |             immutable borrow occurs here
  |         mutable borrow occurs here

在我看来 v 当值 v[v.len() - 1] 计算并传递给 next() . 这意味着 v 将在最外层调用中成功 v.push()

我知道你也可以用迭代器/生成器来实现这一点,但我想知道为什么这会发生在这段特定的代码中,因为这可能是我在某个时候会再次遇到的问题。