[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. 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. I too would like to just do `unknown:` or `unexpected:` but that's technically a source-breaking change: switch foo { case bar: unknown: while baz() { while garply() { if quux() { break unknown } } } } Another downside of the `unexpected case:` spelling is that it doesn't work as part of a larger pattern. I don't have a good answer for that one, but perhaps it's acceptable for now. I'll write up a revision of the proposal soon and make sure the core team gets my recommendation when they discuss the results of the review. --- I'll respond to a few of the more intricate discussions tomorrow, including the syntax of putting a new declaration inside the enum rather than outside. Thank you again, everyone, and happy new year! Jordan
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