[swift-evolution] [Pitch] Allow use of the name "default" for enum cases and function names

[Xiaodi Wu]

Replacing default with case _ is a commonly rejected proposal, and I do
believe it's been discussed since the lowercasing of enum cases.

On Fri, Jun 17, 2016 at 15:55 Tony Allevato via swift-evolution <
swift-evolution at swift.org> wrote:

> Agreed, it sounds like default should be treated as a contextual keyword
> in this case.
>
> It never even occurred to me that "case _:" would work as a replacement
> for default, but it does even today—and now that I've seen it, it makes
> total sense. I could definitely get behind a proposal to remove "default"
> as a keyword from the language entirely in favor of that. It blends well
> with other pattern matching. The only concern I would have would be about
> discoverability, but it would be easy to have the compiler emit an error
> when it sees default in a switch: "default is unsupported; use case _
> instead."
>
>
> On Fri, Jun 17, 2016 at 1:45 PM E. Maloney via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> While upgrading to Swift 3, I noticed that I had a few enums with cases
>> named .Default that, after being converted to lowercase, now need to be
>> rendered using the ugly .`default` notation.
>>
>> I also noticed something similar while reading the docs for
>> NotificationCenter (the NSNotificationCenter replacement, that is, not the
>> NotificationCenter that governs the notification center UI); “default”
>> can’t be used as a function name without escaping, so the declaration is:
>>
>> class func `default`()
>>
>> It seems to me that in the case of function names and enum cases, the
>> parser should be able to unambiguously distinguish between the Swift
>> keyword “default” and a user-defined name “default”, since IIRC the keyword
>> “default” can only be used in parameter lists for generated headers and as
>> the last item in a switch statement.
>>
>> (Perhaps this is also another argument in favor of using “case _:” in
>> place of “default:” in a switch statement.)
>>
>> What do you think? Is there any reason this *wouldn’t* be feasible?
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