[swift-dev] New warning message while switching on an enum

[Jordan Rose]

It's neither a variable binding nor an expression pattern, right? It has to be compared against the original type to know whether it's exhaustive or not. (Consider "let error as NSError" in a catch clause, which should be considered exhaustive.)

Jordan

> On May 9, 2017, at 11:12, Robert Widmann <devteam.codafi at gmail.com> wrote:
> 
> It’s mine, yep.  It looks like it’s classifying the cast in the first pattern as a variable binding instead of an expression pattern.  I’ll push a fix later.
> 
> Thanks!
> 
>> On May 9, 2017, at 1:52 PM, Jordan Rose <jordan_rose at apple.com <mailto:jordan_rose at apple.com>> wrote:
>> 
>> That looks like a bug to me, since of course the first pattern won't always match. I suspect this is Robert's work on trying to make the exhaustive checks better, https://github.com/apple/swift/pull/8908 <https://github.com/apple/swift/pull/8908>. Thanks for catching this!
>> 
>> Jordan
>> 
>> 
>>> On May 9, 2017, at 07:09, Pushkar N Kulkarni via swift-dev <swift-dev at swift.org <mailto:swift-dev at swift.org>> wrote:
>>> 
>>> Hi there, 
>>> 
>>> I see a new warning message for switch statements on enums, like this one: 
>>> 
>>> enum Test {
>>>     case one(Any)
>>>     case two
>>> }
>>> 
>>> let x: Test = .one("One")
>>> switch x {
>>>     case .one(let s as String): print(s)
>>>     case .one: break
>>>     case .two: break
>>> }
>>> 
>>> enum.swift:9:10: warning: case is already handled by previous patterns; consider removing it
>>>     case .one: break 
>>> 
>>> 
>>> I do not see this warning with the 04-24 dev snapshot. 
>>> 
>>> The warning goes away with the use of the wildcard pattern in the second case:
>>> 
>>> switch x {
>>>     case .one(let s as String): print(s)
>>>     case .one(_): break
>>>     case .two: break
>>> }
>>> 
>>> 
>>> I am wondering if this change is intentional, though it does make sense to me. Can someone please point me to the related commit?
>>> 
>>> Thanks in advance!
>>> 
>>> Pushkar N Kulkarni,
>>> IBM Runtimes
>>> 
>>> Simplicity is prerequisite for reliability - Edsger W. Dijkstra
>>> 
>>> 
>>> _______________________________________________
>>> swift-dev mailing list
>>> swift-dev at swift.org <mailto:swift-dev at swift.org>
>>> https://lists.swift.org/mailman/listinfo/swift-dev <https://lists.swift.org/mailman/listinfo/swift-dev>
>> 
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-dev/attachments/20170509/3c501400/attachment.html>