Why are AsyncThrowingStream helpers constrained to Failure == Swift.Error?

[p4checo]

hi @stephencelis and @mbrandonw 👋🏼

Could you please share the reasoning for the AsyncThrowingStream helpers to be constrained to Failure == Swift.Error?

Is there any limitation around using custom error types? I have a faint idea of having read about it somewhere, but I've searched the documentation, GH repos and git history and found no reference of that. Apologies if I missed it.

If there's a limitation then I guess it would be good if it were documented. Otherwise, does it make sense for this restriction be lifted?

Thanks! 🙇🏼

[stephencelis]

@p4checo We're following Apple's lead here: https://developer.apple.com/documentation/swift/asyncthrowingstream/init(_:bufferingpolicy:_:)

They're generic over Failure to prepare for a future where typed throws is supported, but till then it can only be equal to the Error existential.

[p4checo]

Thanks @stephencelis!

Everything makes much more sense now... 😅 I completely missed that restriction on the main init.

Typed throws will IMO fill in a big gap in the language and remove quite a bit of friction. Can't wait for that!