> On Jan 16, 2018, at 10:24 AM, Jordan Rose <jordan_r...@apple.com> wrote:
>>> On Jan 12, 2018, at 3:08 PM, Jordan Rose <jordan_r...@apple.com 
>>> <mailto:jordan_r...@apple.com>> wrote:
>>> Okay, I went back to `unknown case` in the proposal, but mentioned Chris's 
>>> point very specifically: if the compiler emits an error, we should go with 
>>> `case #unknown` instead. (I'm very strongly in the "warning" camp, though.)
>> Thanks!
>> Out of curiosity, why not “unknown default:”?  The “warning” behavior is a 
>> customization of default, so this seems like a more logical model.  It also 
>> fits into the existing Swift grammar, unlike “unknown case:” which requires 
>> adding a new special case production.
> I'm not sure how this fits more into the existing grammar. Both of them 
> require custom parsing with one token's worth of lookahead. You're right that 
> they suggest different natural modelings in the AST, but that's an 
> implementation detail.

The parser has fairly general support for declmodifiers, and my proposal fits 
directly into that.  The only extension is that ‘default’ isn’t a decl, and I 
don’t think we have a statement modifier yet.  That said, we’ve always planned 
to have them when the need arose.

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