[swift-evolution] [Review] SE 0192 - Non-Exhaustive Enums

Jason Merchant jasonmerchant at gmail.com
Wed Jan 3 02:54:38 CST 2018

Is it hard to imagine that most everyone can get what they want and keep
the syntax clean and streamlined at the same time? Without any "@" signs or
other compiler hints?

"Rather, we are how to enable the vendor of a nonexhaustive enum to add new
> cases without breaking binaries compiled against previous versions"

When an enum changes, and the change causes the code to break, the user can
be presented with migration options from an automated IDE tool. In what
specific way does this not solve the issue about having to upgrade your
code when using someone else's code library? This very notion implies your
disgruntled about doing work when things are upgraded, is that really what
this fuss is all about?

A well written language interpreter and auto-tooling IDE would not need
hints embedded in the code syntax itself. Migration hints from version to
version should not be a part of either the past or future version of the
code library.


I don't expect the community to agree on language grammar, but the common
sense here on how to achieve the intended goals seems to be out of wack.

If someone can present a clear logical statement as to how an automated
migration tool behind the scenes in the IDE to handle all your versioning
worries, does not make this whole discussion about adding more convoluted
syntax additions irrelevant, I'd love to hear it.



On Tue, Jan 2, 2018 at 12:36 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:

> On Tue, Jan 2, 2018 at 12:11 PM, Jason Merchant via swift-evolution <
> swift-evolution at swift.org> wrote:
>> I think this whole thing has been unnecessarily convoluted. As a result,
>> the majority of the replies are rabbit holes.
>> In my opinion, the true root of the concept in question is as follows:
>> *A list of something is desired:*
>> 1 - Pancake
>> 2 - Waffle
>> 3 - Juice
>> *Developer wishes to be able to:*
>> *A)* Add new things to the list of choices in the future as they come up
>> with new ideas
>> *B)* Sometimes select one of the choices to be chosen as the normal
>> choice if no choice is made by the user
>> A and B are *separate desires*. In some circumstances a developer may
>> want to add a new choice and make it the normal choice when there was no
>> normal choice was clarified before.
> I don't think this is an accurate summary of the problem being tackled
> here. Rather, we are how to enable the vendor of a nonexhaustive enum to
> add new cases without breaking binaries compiled against previous versions.
> There is little here to do with what a "default" should be. Indeed, it is
> an explicit design decision of Swift not to support types having an
> implicit default value.
>> ____________________
>> *Part 2:*
>> After this simple desire is clear, there should be two discussions:
>> *A)* In a text only coding language, what would we like the syntax to
>> look like? (Without regard to past-bias. What should it really be, forget
>> what mistaken design choices were made in Swift in the past)
>> *B)* How do we approach making this happen behind the scenes?
>> *Bonus:* Given that some of us have changed our approach to programming
>> significantly beyond text based coding, and into more dynamic mediums of
>> programming in other niches, and even here and there in Xcode - I would
>> recommend considering how the IDE would show a modern version of this
>> concept. I feel too often that Swift design syntax has a *lack of
>> awareness between the distinctions of what the IDE should do, as opposed to
>> what the syntax of the language should be*, and what should be handled
>> behind the scenes by automated tooling.
>> _____________________
>> *My opinion*, in answering the above questions is in preference to a
>> simple easy to read and write syntax, something like the following:
>> choices Breakfast {
>>     Pancake, *Waffle*, Juice
>> }
>> If a "default" choice is desired, it is obvious to me that I would select
>> the choice from the IDE, and it would be visually indicated that it was the
>> default.
>> When changes occur, whether new choices are added, old ones are removed
>> or changed, or a default is added, changed, or removed - a behind the
>> scenes automated tool analyzes the changes and presents migration options
>> through the IDE.
>> _____________________
>> Sincerely,
>> Jason
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20180103/e37ed2f9/attachment.html>

More information about the swift-evolution mailing list