Rust 尽管使用了克隆，为什么引用从 lambda 内部泄漏

我试图在使用回调的一段代码中实现CLONE_INTO_BOX模式，但我遇到了一个难以理解的错误.

基本上，我是在克隆lambda的参数，但borrow 判断器仍然抱怨我泄露了对所述参数的引用.

我的问题是:这是borrow 判断器过于保守的情况(如果是这样的话，我如何才能以一种与borrow 判断器很好地配合的方式重写这篇文章)，或者是我在这里遗漏了什么，尽管有克隆，但引用确实被泄露了吗？

代码:

pub trait CloneIntoBox{
    fn clone_into_box<'a>(&self) -> Box<dyn CloneIntoBox + 'a>;
}

impl<'a> Clone for Box<dyn CloneIntoBox + 'a> {
    fn clone(&self) -> Self {
        self.as_ref().clone_into_box()
    }
}

#[derive(Clone)]
pub struct StructWithBox<'a> {
    pub my_box: Box<dyn CloneIntoBox + 'a>,
}

#[derive(Clone)]
struct StructThatCanBeClonedIntoBox {
    pub data: u32,
}

impl CloneIntoBox for StructThatCanBeClonedIntoBox {
    fn clone_into_box<'a>(&self) -> Box<dyn CloneIntoBox + 'a> {
        Box::new(self.clone())
    }
}

pub type WalkCallback<'a> = dyn FnMut(&StructWithBox) + 'a;

pub fn walk(data: Vec<u32>, cb: &mut WalkCallback) {
    for d in data{
        let instance = StructWithBox{my_box: Box::new(StructThatCanBeClonedIntoBox{data:d})};
        cb(&instance);
    }
}

fn main() {
    let data = vec![1, 2];
    let mut result = vec![];
    walk(data, &mut|param| result.push((*param).clone()));
}

[Playground link]个

提供:

error[E0521]: borrowed data escapes outside of closure
  --> src/main.rs:39:28
   |
38 |     let mut result = vec![];
   |         ---------- `result` declared here, outside of the closure body
39 |     walk(data, &mut|param| result.push((*param).clone()));
   |                     -----  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `param` escapes the closure body here
   |                     |
   |                     `param` is a reference that is only valid in the closure body