试着做一些

use std::sync::Arc;
struct Foo(Arc<Bar>);
# [derive(Clone)]
struct Bar;
impl Foo {
    fn bar_mut(&mut self) -> &mut Bar {
        match Arc::get_mut(&mut self.0) {
            Some(bar) => bar,
            None => {
                let new_bar = Bar::clone(&self.0);
                self.0 = Arc::new(new_bar);
                Arc::get_mut(&mut self.0).unwrap()
            }
        }
    }
}
fn main() {
    Foo(Arc::new(Bar)).bar_mut();
}

但我得到以下错误：

* Executing task: cargo check
    Checking testproj v0.1.0 (/home/dspyz/testproj)
error[E0502]: cannot borrow `self.0` as immutable because it is also borrowed as mutable
  --> src/main.rs:13:42
   |
9  |       fn bar_mut(&mut self) -> &mut Bar {
   |                  - let's call the lifetime of this reference `'1`
10 |           match Arc::get_mut(&mut self.0) {
   |           -                  ----------- mutable borrow occurs here
   |  _________|
   | |
11 | |             Some(bar) => bar,
12 | |             None => {
13 | |                 let new_bar = Bar::clone(&self.0);
   | |                                          ^^^^^^^ immutable borrow occurs here
...  |
16 | |             }
17 | |         }
   | |_________- returning this value requires that `self.0` is borrowed for `'1`
error[E0506]: cannot assign to `self.0` because it is borrowed
  --> src/main.rs:14:17
   |
9  |       fn bar_mut(&mut self) -> &mut Bar {
   |                  - let's call the lifetime of this reference `'1`
10 |           match Arc::get_mut(&mut self.0) {
   |           -                  ----------- borrow of `self.0` occurs here
   |  _________|
   | |
11 | |             Some(bar) => bar,
12 | |             None => {
13 | |                 let new_bar = Bar::clone(&self.0);
14 | |                 self.0 = Arc::new(new_bar);
   | |                 ^^^^^^ assignment to borrowed `self.0` occurs here
15 | |                 Arc::get_mut(&mut self.0).unwrap()
16 | |             }
17 | |         }
   | |_________- returning this value requires that `self.0` is borrowed for `'1`
error[E0499]: cannot borrow `self.0` as mutable more than once at a time
  --> src/main.rs:15:30
   |
9  |       fn bar_mut(&mut self) -> &mut Bar {
   |                  - let's call the lifetime of this reference `'1`
10 |           match Arc::get_mut(&mut self.0) {
   |           -                  ----------- first mutable borrow occurs here
   |  _________|
   | |
11 | |             Some(bar) => bar,
12 | |             None => {
13 | |                 let new_bar = Bar::clone(&self.0);
14 | |                 self.0 = Arc::new(new_bar);
15 | |                 Arc::get_mut(&mut self.0).unwrap()
   | |                              ^^^^^^^^^^^ second mutable borrow occurs here
16 | |             }
17 | |         }
   | |_________- returning this value requires that `self.0` is borrowed for `'1`
Some errors have detailed explanations: E0499, E0502, E0506.
For more information about an error, try `rustc --explain E0499`.
error: could not compile `testproj` due to 3 previous errors

• 终端进程“货'检'"启动失败（退出代码：101页）。
• 终端将被任务重复使用，按任意键关闭它。