[swift-evolution] Enums and Source Compatibility

Goffredo Marocchi panajev at gmail.com
Sat Sep 16 04:22:27 CDT 2017


I am still unsure why we are choosing again a default that protects library writers more than library users where it is reasonable to expect the former to have better mastery of the language, to architect a library with some scalability, and ability to add unit test to cover themselves from issues than the latter.

Exhaustive and open by default with keywords to close things down if the framework author wants them.

Sent from my iPhone

> On 16 Sep 2017, at 09:55, David Hart via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I’m still very much bothered by having 2 new keywords. I would really prefer the following plan:
> 
> Exhaustive by default in Swift 4
> No new keyword in Swift 4 to change that behaviour
> Non-exhaustive by default outside the module in Swift 5
> exhaustive keyword to change the default behaviour
> 
> Like that, we don’t need nonexhaustive.
> 
> Thoughts?
> David.
> 
>> On 13 Sep 2017, at 21:16, Jordan Rose via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> Proposal updated, same URL: https://github.com/jrose-apple/swift-evolution/blob/non-exhaustive-enums/proposals/nnnn-non-exhaustive-enums.md.
>> 
>> Thanks again for all the feedback so far, everyone!
>> Jordan
>> 
>> 
>>> On Sep 12, 2017, at 17:55, Jordan Rose via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>> Sorry, I got distracted by other tasks! Both the discussion here and within Apple has moved towards making "non-exhaustive" the default, which, to be honest, I too think is the best design. I'll update the proposal today to reflect that, though I still want to keep both the "nonexhaustive" and "exhaustive" keywords for Swift 4 compatibility for now (or whatever we end up naming them). The compatibility design is a little less ambitious than Brent's; as currently proposed, Swift 4 mode continues to default to 'exhaustive' all the time, even in the actual Swift 5 release.
>>> 
>>> I still want to respond to Brent's points directly, but I think you and Vladimir have done a good job discussing them already. I'll send out the updated proposal tomorrow, after I have a little more time to think about #invalid.
>>> 
>>> Thanks for putting time into this!
>>> Jordan
>>> 
>>> 
>>>> On Sep 9, 2017, at 17:34, Rod Brown <rodney.brown6 at icloud.com> wrote:
>>>> 
>>>> Jordan,
>>>> 
>>>> Do you have any other thoughts about the ongoing discussion here, especially regarding Chris’ comments? As you’re the one pushing this forward, I’d really like to know what your thoughts are regarding this?
>>>> 
>>>> - Rod
>>> 
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