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

[Goffredo Marocchi]

> On 5 Jan 2018, at 00:38, Jordan Rose via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Furthermore, the old code needs to continue working without source changes, because updating to a new SDK must not break existing code. (It can introduce new warnings, but even that is something that should be considered carefully.)
> 
> So: this proposal is designed to handle the use cases both for Swift library authors to come and for C APIs today, and in particular Apple's Objective-C SDKs and how they've evolved historically.

I will let your very comprehensive rationale brew a little bit more in my mind and reread it, but I still think this is a bit leaning too much over to library authors than library consumers (not unlike the closed by default discussion we all had a while ago).

I remain very unconvinced by the “updating library/SDK” must be source compatible. Especially if it is major version change and a deprecated method has been removed, methods have changed signature, etc... Backward compatible runtime with code compiled against the previous SDK yes, source compatible no.

I feel like this change will make the life easier for library authors, but risks making it easier and easier to make mistakes in apps using the libraries: exhaustive switching over enums is a good important feature that risks going away (the default matters) for not a huge effective benefit to app developers.
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