Synchronous Swift methods cannot throw errors

[mrousavy]

In a synchronous method inside of a Swift HybridObject, you cannot throw any errors because they are not propagated upwards to C++.

The previous workaround used result types (.success(value) or .failure(error)) instead of exceptions, but those will be caught and wrapped anyways. This didn't work because of a Swift compiler bug where arrays/generics couldn't be used inside enums, so we could only support primitives.

A workaround would be to just return a Promise<..>, then you can throw inside there which will be a promise rejection.

[mrousavy]

created a PR to finally fix this: #430

was definitely not easy lol