compilation failure with ambiguous associated item when enum has variant called Error

[mlwilkerson]

Describe the Bug

Recently, I started seeing an error message during compilation on a simple enum with the #[wasm_bingen] attribute macro. The significant detail about the macro is that it includes a variant named Error.

Here's the compilation error message:

error: ambiguous associated item
   --> tests/wasm/enums.rs:74:1
    |
74  | #[wasm_bindgen]
    | ^^^^^^^^^^^^^^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #57644 <https://github.com/rust-lang/rust/issues/57644>
note: `Error` could refer to the variant defined here
   --> tests/wasm/enums.rs:79:5
    |
79  |     Error,
    |     ^^^^^
note: `Error` could also refer to the associated type defined here
   --> /Users/someuser/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/convert/mod.rs:641:5
    |
641 |     type Error;
    |     ^^^^^^^^^^
    = note: `#[deny(ambiguous_associated_items)]` on by default
    = note: this error originates in the attribute macro `wasm_bindgen` (in Nightly builds, run with -Z macro-backtrace for more info)

Steps to Reproduce

1. create an enum like this:

#[wasm_bindgen]
#[derive(Copy, Clone)]
pub enum EnumWithErrorVariant {
    OK,
    Warning,
    Error,
}

2. compile it using rust 1.72 or 1.73, with wasm-bindgen 0.2.88

Expected Behavior

Compilation with no errors

Actual Behavior

Compilation error

Prototype

I found that the compilation error was eliminated when changing this codegen:

        impl wasm_bindgen::__rt::core::convert::TryFrom<wasm_bindgen::JsValue>
        for EnumWithErrorVariant {
            type Error = wasm_bindgen::JsValue;
            fn try_from(
                value: wasm_bindgen::JsValue,
            ) -> wasm_bindgen::__rt::std::result::Result<Self, Self::Error> {
        //...snip...
      }

To this:

impl wasm_bindgen::__rt::core::convert::TryFrom<wasm_bindgen::JsValue> for EnumWithErrorVariant {
    type Error = wasm_bindgen::JsValue;
    fn try_from(
        value: wasm_bindgen::JsValue,
    ) -> wasm_bindgen::__rt::std::result::Result<
        Self,
        <EnumWithErrorVariant as TryFrom<JsValue>>::Error,
    > {
//...snip...
}

Notice the Error type in the return Result is <EnumWithErrorVariant as TryFrom<JsValue>>::Error instead of Self::Error

This based on the guidance indicated by the rust issue linked in the error message:
rust-lang/rust#57644

[mlwilkerson]

The linked PR includes a reproduction of the bug within this repo's wasm test suite, along with a proposed fix.

[bastibense]

Ahh, I stumbled across this while porting some code to Rrust. One of the enum values was named Error so the compiler got confused. 😓