`isVoidReturn` should be exposed

[gmpassos]

Since the use of the inner Function should be allowed, it's important to be able to check if the returned value is void.

[juancastillo0]

Hi thanks for the issue!

On native platforms you can use the WasmFunction.results.length to check whether a function returns something.

On web you can use js_util.typeofEquals<dynamic>(result, 'undefined') to check whether the return is undefined. Before Dart 3.0 I think you need to use the following code for web (in wasm_run we use both methods):

bool isVoidReturn(dynamic value) {
  switch (value) {
    case null:
      return false;
    default:
      return value == null;
  }
}

Although we can could expose it I don't feel it's necessary. But I could be wrong, please let me know if those methods workd for you or if you think we should expose isVoidReturn.

Thanks