[Pitch N+1] Typed Throws

[Karl]

@Douglas_Gregor

Swift language version 6, which we'll refer to herein as Swift 6, offers an opportunity to introduce a targeted set of source-incompatible changes to the language. Swift 6 must not change the fundamental shape of the language, nor make sweeping changes without purpose. Rather, it should only introduce changes that serve a specific goal that benefits the entire Swift ecosystem and is not achievable while maintaining source compatibility.

@Douglas_Gregor

The Language Workgroup will evaluate on a case-by-case basis any additional changes that provide sufficiently high value to the language relative to the cost of source incompatibilities they introduce. For example, Swift 6 may include proposals with source-incompatible changes where they are needed to finish a feature that cannot be completed otherwise, such as the regex literal parsing changes in SE-0354 or the requirement for 'any' on existential types introduced in SE-0335 .

I'm not really sure exactly what is being discussed here -- the removal of rethrows? Or just general observations that a similar concept may be expressible in another way? I read the discussion, but I still can't tell exactly.

If it is the former, I hope it comes with some very, very compelling reasons for breaking source compatibility. Especially since, as has been noted, this "other way" is not an exact 1:1 replacement for the existing rethrows feature. That means there may be libraries which cannot implement that other way without breaking their APIs.