Generate Box<Fn()> error

[lbhfuture]

Describe the bug

1. Write Rust code with a Fn running in tokio::spawn, as below:

   pub async fn start(&self, callback: Box<dyn Fn() -> DartFnFuture<bool> + Send>) {
       tokio::spawn(async move {
           loop {
               callback().await;
           }
       });
   }

2. Then the FRB generated codes as below:

   
   Future<void> start({required BoxFnDartFnFutureBool callback});

abstract class BoxFnDartFnFutureBool implements RustOpaqueInterface {}

3. When I use the `start` function in Dart, I cannot return a bool value in the `callback`. Is it a bug, or how can I use the `start` function correctly? The analyzer error report is `The argument type 'Future<bool> Function()' can't be assigned to the parameter type 'BoxFnDartFnFutureBool'.`.

### Steps to reproduce

Just do as the description above.

### Logs

```shell
No logs.

Expected behavior

No response

Generated binding code

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OS

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Version of flutter_rust_bridge_codegen

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Flutter info

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Version of clang++

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Additional context

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[xuxiaocheng0201]

Try callback: impl Fn() -> DartFnFuture<bool> + Send?

[fzyzcjy]

Totally agree with @xuxiaocheng0201, maybe have a try about that :)

[lbhfuture]

I use callback: impl Fn() -> DartFnFuture<bool> + Send + 'static works, thanks.