Rust 为什么父作用域中的变量超出了子作用域

我在理解Rust 的范围时遇到了问题.我try 实现一个简单的代码来播放声音.我想填充缓冲区然后播放它，但我无法让它编译.

我得到了这个方法:

fn main() {
    let channels: usize = 2;
    let device = initialize_device();
    let config = initialize_configuration(&device, channels as u16);

    let mut stream_buffer = [0.0 as f32; 64];
    {
        let mut oscillator = Oscillator::new(440.0 as f32, 0.0 as f32, 44100.0 as f32, &mut stream_buffer);

        let processor = move |_data: &mut [f32], _: &cpal::OutputCallbackInfo| {
            //FIXME: Send data from oscillator to _data
            oscillator.process();
        };
    
        let stream = build_outputstream(config, device, Box::new(processor));

        let _ = stream.play();

        std::thread::sleep(std::time::Duration::from_millis(2000));
    }
}

变量"stream_buffer"位于作用域之前

    let mut stream_buffer = [0.0 as f32; 64];
    {
        ...
    }

在那里执行其余代码.

根据我从rust文档中了解到的情况，默认情况下，变量位于堆栈上，我们可以将它们装箱以将它们放在堆上. 因此，stream_buffer位于堆栈上，并且应该保留在堆栈上直到程序结束.即使我没有手动创建它下面的范围.

该文档还表示，堆上的变量在超出范围时会自动销毁. 所以，我知道我的盒装processor的生命周期比stream_buffer短，并且它在其范围结束时被销毁.

 let mut stream_buffer = [0.0 as f32; 64];
    {
        let mut oscillator = Oscillator::new(440.0 as f32, 0.0 as f32, 44100.0 as f32, &mut stream_buffer);

        let processor = move |_data: &mut [f32], _: &cpal::OutputCallbackInfo| {
            //FIXME: Send data from oscillator to _data
            oscillator.process();
        };
    
        let stream = build_outputstream(config, device, Box::new(processor));
        ...
    }

但编译器抱怨"stream_buffer"不够活跃.

error[E0597]: `stream_buffer` does not live long enough
  --> src\main.rs:42:88
   |
40 |     let mut stream_buffer = [0.0 as f32; 64];
   |         ----------------- binding `stream_buffer` declared here
41 |     {
42 |         let mut oscillator = Oscillator::new(440.0 as f32, 0.0 as f32, 44100.0 as f32, &mut stream_buffer);
   |                                                                                        ^^^^^^^^^^^^^^^^^^ borrowed value does not live long enough
...
49 |         let stream = build_outputstream(config, device, Box::new(processor));
   |                                                         ------------------- cast requires that `stream_buffer` is borrowed for `'static`
...
55 | }
   | - `stream_buffer` dropped here while still borrowed
   |
   = note: due to object lifetime defaults, `Box<dyn for<'a, 'b> FnMut(&'a mut [f32], &'b OutputCallbackInfo) + Send>` actually means `Box<(dyn for<'a, 'b> FnMut(&'a mut [f32], &'b OutputCallbackInfo) + Send + 'static)>`

如果我按照编译器建议的那样将stream_buffer设置为静态，它就会起作用.但我不想. 我想我明白，因为处理器必须在堆上，所以我别无 Select ，只能让stream_buffer保持静态？我不能把stream_buffer放在堆栈上，把处理器放在堆上吗？