Nullable return types

[dbrgn]

This example builds:

#[wasm_bindgen]
pub struct Hello {
    pub a: u32,
}

#[wasm_bindgen]
pub fn say_hello() -> Hello {
    Hello { a: 42 }
}

But when changin the return type of say_hello to an Option, it fails:

#[wasm_bindgen]
pub struct Hello {
    pub a: u32,
}

#[wasm_bindgen]
pub fn say_hello() -> Option<Hello> {
    Some(Hello { a: 42 })
}

Error:

  error[E0277]: the trait bound `Hello: wasm_bindgen::convert::traits::OptionIntoWasmAbi` is not satisfied
    --> examples/hello_world/src/lib.rs:18:1
     |
  18 | #[wasm_bindgen]
     | ^^^^^^^^^^^^^^^ the trait `wasm_bindgen::convert::traits::OptionIntoWasmAbi` is not implemented for `Hello`
     |
     = note: required because of the requirements on the impl of `wasm_bindgen::convert::traits::IntoWasmAbi` for `std::option::Option<Hello>`

  error: aborting due to previous error

Is this not supported? I would have expected Hello | null as return type.

[dbrgn]

@alexcrichton any chance of a new release soon?

[remram44]

+1. I've been using the Git repo as dependency (using [patch]), but I also have to install the cli from Git, which is awkward (especially for CI).

[alexcrichton]

Sure thing!

[dbrgn]

Thanks! ❤️