> On 16 Sep 2017, at 7:22 pm, Goffredo Marocchi via swift-evolution > <swift-evolution@swift.org> wrote: > > 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.
Because protecting library owners protects library users. If you declare it is exhaustive and it was an oversight, and then realise after the fact that you are wrong, you have to open it up. This will break third party apps. It will be disallowed by the ABI compatibility requirements. If you declare it isn’t exhaustive due to an oversight (or perhaps you’re just not sure yet), and then realise after the fact it is exhaustive, you can close it up. This will not break third party apps. It will also be allowed for ABI compatibility. This benefits everyone. Make library owners choose a guarantee, rather than be defaulted into it. Much like they have to declare choose to declare “final” on a class: you can’t retroactively reneg that promise: it will break everyone who assumed it to be the case! > > 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@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@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@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.bro...@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 >>>> >>>> _______________________________________________ >>>> swift-evolution mailing list >>>> swift-evolution@swift.org >>>> https://lists.swift.org/mailman/listinfo/swift-evolution >>> >>> _______________________________________________ >>> swift-evolution mailing list >>> swift-evolution@swift.org >>> https://lists.swift.org/mailman/listinfo/swift-evolution >> >> _______________________________________________ >> swift-evolution mailing list >> swift-evolution@swift.org >> https://lists.swift.org/mailman/listinfo/swift-evolution > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution
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