> On 3 Jan 2018, at 02:07, Jordan Rose wrote: > > [Proposal: > https://github.com/apple/swift-evolution/blob/master/proposals/0192-non-exhaustive-enums.md > > <https://github.com/apple/swift-evolution/blob/master/proposals/0192-non-exhaustive-enums.md>] > > Whew! Thanks for your feedback, everyone. On the lighter side of > feedback—naming things—it seems that most people seem to like '@frozen', and > that does in fact have the connotations we want it to have. I like it too.
Should there be a new Clang attribute for "frozen" enums? Then the existing `__attribute__((enum_extensibility(closed)))` would only prevent "private" cases (and not future "public" cases). <https://clang.llvm.org/docs/AttributeReference.html#enum-extensibility-clang-enum-extensibility> > More seriously, this discussion has convinced me that it's worth including > what the proposal discusses as a 'future' case. The key point that swayed me > is that this can produce a warning when the switch is missing a case rather > than an error, which both provides the necessary compiler feedback to update > your code and allows your dependencies to continue compiling when you update > to a newer SDK. I know people on both sides won't be 100% satisfied with > this, but does it seem like a reasonable compromise? > > The next question is how to spell it. I'm leaning towards `unexpected case:`, > which (a) is backwards-compatible, and (b) also handles "private cases", > either the fake kind that you can do in C (as described in the proposal), or > some real feature we might add to Swift some day. `unknown case:` isn't bad > either. You might end up with `case .unknown:` and `unknown case:` in the same switch. e.g. <https://developer.apple.com/documentation/photos/phassetmediatype> ``` switch mediaType { case .image, .video, .audio: break case .unknown: break unknown case: break } ``` -- Ben
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