[swift-evolution] Warning when omitting default case for imported enums

[Rien]

I have no objection against removing that warning.
The warning seems unnecessary to me.

Regards,
Rien

Site: http://balancingrock.nl
Blog: http://swiftrien.blogspot.com
Github: http://github.com/Balancingrock
Project: http://swiftfire.nl





> On 07 Feb 2017, at 22:13, Tanner Nelson <tanner at qutheory.io> wrote:
> 
> Adding a default case when you've exhaustively switched on the enum results in a warning currently. The default case is not really optional at that point if you want to compile without warnings. 
> 
> ```
> warning: default will never be executed default: break
> ```
> 
> Sent from my iPhone
> 
>> On Feb 7, 2017, at 20:13, Christopher Kornher <ckornher at me.com> wrote:
>> 
>> -1 This warning suggestion is of highly questionable value. Authors are free to add a default case or not, depending upon the nature of the enum and the logic to handle them. There is no “right” way to suggest, although for high-reliability code, default cases should usually be avoided in my opinion.
>> 
>> 
>>> On Feb 7, 2017, at 11:49 AM, Rien via swift-evolution <swift-evolution at swift.org> wrote:
>>> 
>>> If you don’t want the default case, and if you like a warning free compilation, you need a way to suppress the warning.
>>> 
>>> Regards,
>>> Rien
>>> 
>>> Site: http://balancingrock.nl
>>> Blog: http://swiftrien.blogspot.com
>>> Github: http://github.com/Balancingrock
>>> Project: http://swiftfire.nl
>>> 
>>> 
>>> 
>>> 
>>> 
>>>> On 07 Feb 2017, at 19:42, Tanner Nelson <tanner at qutheory.io> wrote:
>>>> 
>>>> I don't understand the part about warning suppression. The warning would go away when you add the default case. 
>>>> 
>>>> Sent from my iPhone
>>>> 
>>>>> On Feb 7, 2017, at 16:25, Rien <Rien at Balancingrock.nl> wrote:
>>>>> 
>>>>> -1
>>>>> 
>>>>> Reason 1: the “negative” behaviour you describe is actually exactly what I want to happen.
>>>>> Reason 2: Introducing a warning would also necessitate a warning suppression in order to have your code compile without warnings. But when you suppress, the purpose of the warning is nul and void.
>>>>> 
>>>>> PS: I would suggest not to use an enum in cases where this is really annoying and replace the enums with constants.
>>>>> 
>>>>> Regards,
>>>>> Rien
>>>>> 
>>>>> Site: http://balancingrock.nl
>>>>> Blog: http://swiftrien.blogspot.com
>>>>> Github: http://github.com/Balancingrock
>>>>> Project: http://swiftfire.nl
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>>> On 07 Feb 2017, at 16:12, Tanner Nelson via swift-evolution <swift-evolution at swift.org> wrote:
>>>>>> 
>>>>>> Hello Swift Evolution,
>>>>>> 
>>>>>> I'd like to propose that a warning be emitted when default cases are omitted for enums from other modules. 
>>>>>> 
>>>>>> What this would look like:
>>>>>> 
>>>>>> OtherModule:
>>>>>> ```
>>>>>> public enum SomeEnum {
>>>>>> case one
>>>>>> case two
>>>>>> }
>>>>>> 
>>>>>> public let global: SomeEnum = .one
>>>>>> ```
>>>>>> 
>>>>>> executable:
>>>>>> ```
>>>>>> import OtherModule
>>>>>> 
>>>>>> switch OtherModule.global {
>>>>>> case .one: break
>>>>>> case .two: break
>>>>>> ^~~~~ ⚠︎ Warning: Default case recommended for imported enums. Fix-it: Add `default: break`
>>>>>> }
>>>>>> ```
>>>>>> 
>>>>>> Why:
>>>>>> 
>>>>>> Allowing the omission of a default case in an exhaustive switch makes the addition of a new case to the enum a breaking change. 
>>>>>> In other words, if you're exhaustively switching on an enum from an imported library, the imported library can break your code by adding a new case to that enum (which the library authors may erroneously view as an additive/minor-bump change).
>>>>>> 
>>>>>> Background:
>>>>>> 
>>>>>> As a maintainer of a Swift framework, public enums have been a pain point in maintaining semver. They've made it difficult to implement additive features and have necessitated the avoidance of enums in our future public API plans.
>>>>>> 
>>>>>> Related Twitter thread: https://twitter.com/tanner0101/status/796860273760104454
>>>>>> 
>>>>>> Looking forward to hearing your thoughts.
>>>>>> 
>>>>>> Best,
>>>>>> Tanner
>>>>>> 
>>>>>> Tanner Nelson
>>>>>> Vapor 
>>>>>> +1 (435) 773-2831
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
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>>>>>> swift-evolution mailing list
>>>>>> swift-evolution at swift.org
>>>>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>>>> 
>>> 
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