#[wasm_bindgen] fails if an enum variant has a #[cfg(xxx)] that evaluates to false

[0xd4d]

#[wasm_bindgen] fails if an enum variant has a #[cfg(xxx)] that evaluates to false

Same thing with structs.

wasm-bindgen = "0.2.59"

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub enum MyEnum {
	#[cfg(feature = "zero")]
	Zero,
}

#[wasm_bindgen]
pub struct MyStruct {
    #[cfg(feature = "field")]
    pub field: u32,
}

Errors:

• error[E0605]: non-primitive cast: MyEnum as u32
• error[E0599]: no variant or associated item named Zero found for enum MyEnum in the current scope
• error[E0609]: no field field on type wasm_bindgen::__rt::Ref<'_, MyStruct>

error[E0605]: non-primitive cast: `MyEnum` as `u32`
 --> src\lib.rs:3:1
  |
3 | #[wasm_bindgen]
  | ^^^^^^^^^^^^^^^
  |
  = note: an `as` expression can only be used to convert between primitive types. Consider using the `From` trait

error[E0599]: no variant or associated item named `Zero` found for enum `MyEnum` in the current scope
 --> src\lib.rs:6:2
  |
4 | pub enum MyEnum {
  | --------------- variant or associated item `Zero` not found here
5 |     #[cfg(feature = "zero")]
6 |     Zero,
  |     ^^^^ variant or associated item not found in `MyEnum`

error[E0609]: no field `field` on type `wasm_bindgen::__rt::Ref<'_, MyStruct>`
  --> src\lib.rs:12:9
   |
12 |     pub field: u32,
   |         ^^^^^ unknown field

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0599, E0605, E0609.
For more information about an error, try `rustc --explain E0599`.

[alexcrichton]

Thanks for the report! This'll probably require some macro-fu to make sure that the #[cfg] on each variant/fields gets to the right locations, since right now we'll probably keep the attribute on the field but we won't apply the attribute to all code that handles the field. The best workaround for now would be to put #[cfg] on the enum itself and define the enum twice, but I know that's unfortunately not great :(

[jbr]

Is this issue up to date? Redefining the enum multiple times isn't easily typed when there are a lot of enum variants that need to be feature-configured. Is there another workaround? How hard would this be to take on as a first wasm-bindgen issue?

[jbr]

I believe this might be resolved by rust-lang/rust#82679