[swift-evolution] #selector and Void methods

[Douglas Gregor]

> On Mar 23, 2016, at 10:14 AM, Jordan Rose via swift-evolution <swift-evolution at swift.org> wrote:
> 
>> 
>> On Mar 23, 2016, at 10:11, Joe Groff via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>>> 
>>> On Mar 22, 2016, at 8:49 PM, Brent Royal-Gordon via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> So, today is day 2 of Swift 2.2 being in the hands of mere mortals. This evening, I walked into my weekly NSCoder Night meeting and talked to a pretty experienced developer struggling with this:
>>> 
>>> 	class EditEventViewController: UIViewController {
>>> 		...
>>> 		@IBAction func cancel(sender: AnyObject?) {
>>> 			cancel()
>>> 		}
>>> 		func cancel() {
>>> 			// actual canceling logic is here
>>> 		}
>>> 	}
>>> 	
>>> 	class EditEventContainerViewController: UIViewController {
>>> 		...
>>> 		func prepareForSegue(_ segue: UIStoryboardSegue, sender sender: AnyObject?) {
>>> 			switch segue.identifier {
>>> 				...
>>> 				let cancelButton = UIBarButtonItem(barButtonSystemItem: .Cancel, target: nil, action: nil)
>>> 				cancelButton.target = vc
>>> 				cancelButton.action = #selector(vc.cancel)	// This is the problem line
>>> 				...
>>> 			}
>>> 		}
>>> 	}
>>> 		
>>> `vc.cancel` was, of course, ambiguous, and the SE-0021 `vc.cancel(_:)` syntax can't select a Void function. I had to explain how to use `as Void -> Void` to select the right version.
>>> 
>>> This is merely an anecdote, but I think it may end up being an issue.
>> 
>> Thanks for reporting this. I also saw this come up at least one other place:
>> 
>> https://twitter.com/bendodson/status/712208662933200896 <https://twitter.com/bendodson/status/712208662933200896>
>> 
>> I wonder if it's worth making #selector(vc.cancel()) work. What do you think, Doug?
> 
> Very strong +1; I consider it a bug that we didn't have this already. It was reported as SR-1016 <https://bugs.swift.org/browse/SR-1016>.

Yes, I agree.

	- Doug


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