Returning closures from the start function fails when using #[wasm_bindgen(start)]

[johnsonw]

The update_from_js example shows how to create closures in rust and make them available in javascript:

#[wasm_bindgen]
pub fn start() -> Box<[JsValue]> {
    let app = App::start("app", init, update, view);
    create_closures_for_js(&app)
}

This works fine in the example, but our start function will generally use #[wasm_bindgen(start)] to make it immediately available to the application. The wasm-bindgen docs state that when using start, we can only return unit or a result: https://rustwasm.github.io/wasm-bindgen/reference/attributes/on-rust-exports/start.html.

The start function must take no arguments and must either return () or Result<(), JsValue>

But the seed docs state (https://seed-rs.org/0.8.0/start):

The official docs are a bit wrong - the function tagged with #[wasm_bindgen(start)] can also return all types that wasm_bindgen can transform to a consumable form for JS. In practice, this means you can return everything that implements FromWasmAbi. See e.g. Box<[JsValue]> in update_from_js example

When using the following in my seed application:

#[wasm_bindgen(start)]
pub fn start() -> Box<[JsValue]> {
    let app = App::start("app", init, update, view);
    create_closures_for_js(&app)
}

I get the following error:

error[E0277]: the trait bound `Box<[seed::prelude::JsValue]>: seed::prelude::wasm_bindgen::__rt::Start` is not satisfied
   --> src/lib.rs:700:1
    |
700 | #[wasm_bindgen(start)]
    | ^^^^^^^^^^^^^^^^^^^^^^ the trait `seed::prelude::wasm_bindgen::__rt::Start` is not implemented for `Box<[seed::prelude::JsValue]>`
    |
    = note: this error originates in the attribute macro `wasm_bindgen`

I'm hoping that I may be missing something but I believe wrapping wasm_bindgen in start is required as when I compile without it the package files contain errors. Being able to return closures appears to be the key piece when tying web_sys callbacks into the messaging system. Am I missing anything here?