Overload function names for use in JS

[devrosch]

Summary

The documentation explains very well how to use polymorphic, i.e., overloaded, JavaScript functions in Rust with js_name.

Is a way to do it the other way around too and make multiple Rust functions available to JS under the same name but with different arguments?

Additional Details

Here is minimalistic example that fails to compile.

use js_sys::Uint8Array;
use wasm_bindgen::prelude::wasm_bindgen;
use web_sys::Blob;

#[wasm_bindgen(js_name = Scanner)]
pub struct JsScanner {}

#[wasm_bindgen(js_class = Scanner)]
impl JsScanner {
    #[wasm_bindgen(constructor)]
    pub fn new() -> JsScanner {
        JsScanner {}
    }

    #[wasm_bindgen(js_name = isRecognized)]
    pub fn js_is_recognized_blob(input: &Blob) -> bool {
        todo!()
    }

    #[wasm_bindgen(js_name = isRecognized)]
    pub fn js_is_recognized_uint8array(input: &Uint8Array) -> bool {
        todo!()
    }
}

The error is:

error: symbol `scanner_isRecognized` is already defined
 --> src/lib.rs:8:1
  |
8 | #[wasm_bindgen(js_class = Scanner)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in the attribute macro `wasm_bindgen::prelude::__wasm_bindgen_class_marker` (in Nightly builds, run with -Z macro-backtrace for more info)

If any one of the the #[wasm_bindgen(js_name = isRecognized)] names are changed the error does not appear. For symmetry with using polymorphic JS functions, it would be very nice to have this work. This question is somewhat related to #1139 but the case here is a bit simpler, I believe.

Is there a way to make this work? Alternatively, is there any workaround?

Thank you for any input on this!

[daxpedda]

You could just take JsValues as arguments and figure out which type it is at runtime, but otherwise this isn't supported.

I'm going to close this in favor of #1339, while it is true that this proposal is a bit simpler, the implementation would be the same and its just API design at this point.