[swift-evolution] [pitch] make @nonobjc the default

[Douglas Gregor]

> On Oct 19, 2016, at 10:37 AM, Joe Groff <jgroff at apple.com> wrote:
> 
>> 
>> On Oct 19, 2016, at 9:35 AM, Douglas Gregor via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> 
>>> On Oct 19, 2016, at 4:53 AM, Jay Abbott <jay at abbott.me.uk <mailto:jay at abbott.me.uk>> wrote:
>>> 
>>> Ok, good to know that's just a bug. But I still think that implicit @objc should be removed. 
>> 
>> Oh, I agree that implicit @objc should be removed. I suspect it’s responsible for a nontrivial amount of code bloat and unnecessary Objective-C selector collisions.
>> 
>>> For bridged classes with obj-c-specific interfaces (for example a method that takes a selector), it would be better if the Swift-side interface was forced to make a Swifty interface that hides it. This way, the people maintaining an interface have to either a) write a wrapper with a Swifty interface; or b) explicitly cop out and use @objc and inform their users that they may also have to do the same in some situations; or c) persuade their employers to let them port the whole thing to pure Swift, which sounds like a lot of fun and is probably what they really want to do :D.
>> 
>> I don’t quite view explicit @objc as a cop-out—it’s a useful tool to limit the amount of glue code one needs to write.
>> 
>>> I'm not really sure how this works though, at what level this is applied? Maybe it's more to do with the default build settings in Xcode than Swift itself? I just would rather see Swift stand alone by default.
>> 
>> I think it’s a Swift language change: we should only infer ‘@objc’ when the API
>> 
>> 	* Overrides of an @objc API,
>> 	* Satisfies a requirement of an @objc protocol, or
>> 	* Uses a Swift feature that requires the Objective-C runtime (e.g., @NSManaged, @IBAction, currently ‘dynamic’ although that feels wrong to me)
> 
> It might also be nice if referring to a method with #selector automatically tried to make it @objc.

It might, although I don’t love the impact on the implementation: we either end up creating one-off categories associated with the references to non- at objc methods or our type checker has to process function bodies to answer the question “is this method exposed to Objective-C”?

	- Doug


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