这是《Rust实战》中的2.7项目，我创建了一个项目，然后也下载了num放入了cargo.toml。 代码检查了一下也没有问题，但对应书上的代码会报错，可能是所有权的问题，请大佬们帮忙看看。

Code

use num::complex::Complex;



fn calculate_mandelbrot(

    max_iters: usize,
    x_min: f64,
    x_max: f64,
    y_min: f64,
    y_max: f64,
    width: usize,
    height: usize,
) -> Vec<Vec<usize>> {
    let mut rows: Vec<_> = Vec::with_capacity(width);
    for img_y in 0..height {
        let mut row: Vec<usize> = Vec::with_capacity(height);
        for img_x in 0..width {
            let x_percent = img_x as f64 / width as f64;
            let y_percent = img_y as f64 / height as f64;
            let cx = x_min + (x_max - x_min) * x_percent;
            let cy = y_min + (y_max - y_min) * y_percent;
            let escaped_at = mandelbrot_at_point(cx, cy, max_iters);
            row.push(escaped_at);

        }
        all_rows.push(row);
    }
    rows
}

fn mandelbrot_at_point(
    cx: f64,
    cy: f64,
    max_iters: usize,
) -> usize {
    let mut z = Complex { re: 0.0, im: 0.0 };
    let c = Complex::new(cx, cy);

    for i in 0..=max_iters {
        if z.norm() > 2.0 {
            return i;
        }
        z = z * z + c;
    }
    max_iters
}

fn render_mandelbrot(escape_vals: Vec<Vec<usize>>) {
    for row in escape_vals {
        let mut line = String::with_capacity(row.len());
        for column in row {
            let val = match column {
                0..=2 => ' ',
                2..=5 => '.',
                5..=10 => '·',
                11..=30 => '*',
                30..=100 => '+',
                100..=200 => 'X',
                200..=400 => '$',
                400..=700 => '#',
                _ => '%',
            };

        line.push(val);
        }
        println!("{line}");
    }
}
fn main() {
    let mandelbrot = calculate_mandelbrot(1000, 2.0, 1.0, -1.0, 1.0, 100, 24);
    render_mandelbrot(mandelbrot);
}

Cargo build

   Compiling mandelbrot v0.1.0 (E:\Cx_Blog\11.rust\mandelbrot)
error[E0425]: cannot find value `all_rows` in this scope
  --> src\main.rs:25:13
   |
25 |             all_rows.push(row);
   |             ^^^^^^^^ not found in this scope

For more information about this error, try `rustc --explain E0425`.
error: could not compile `mandelbrot` due to previous error