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

[Douglas Gregor]

> On Oct 19, 2016, at 4:53 AM, Jay Abbott <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’s hard to justify pushing for this in Swift 4 stage 1, because changing defaults doesn’t affect the ABI, but it’s something I’d love to see us do at some point in Swift 4.

	- Doug

> 
> 
> 
> On Wed, 19 Oct 2016 at 03:51 Douglas Gregor <dgregor at apple.com <mailto:dgregor at apple.com>> wrote:
> 
> 
> Sent from my iPhone
> 
> > On Oct 18, 2016, at 4:00 PM, Jay Abbott via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> >
> > Currently, if you extend a class that comes from obj-c, Swift assumes you want to make those methods available to call from obj-c code. If you add operators, you must declare them as @nonobjc otherwise the bridging header which is generated declares obj-c methods with the operator character as the method name, which isn't valid in obj-c and causes compile errors.
> 
> The operators bit is an outright bug, which I believe has already been fixed in master.
> 
> > I'm just wondering how others feel about this - my feeling is that a Swift developer should not have to know anything about obj-c when doing Swifty things to a bridged class from a framework (such as extending it). As far as they are concerned the framework class should compile the same as if it were fully implemented in Swift.
> 
> Modulo bugs like the above, I think we already have this property? Swift declarations are exposed to Objective-C if they can be. One doesn't generally have to think about it unless you're trying to use those declarations from Objective-C.
> 
> > Thoughts?
> 
> I actually thought you were going further with this, eliminating the inferred @objc except in cases where it's needed to work with an existing framework. That's something I'd love to see someone working on.
> 
>   - Doug
> 

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