[swift-users] Capturing difference with typealias

[Slava Pestov]

Hi Jon,

In beta 6, non-escaping is now the default, and you must use the @escaping attribute to declare a parameter as escaping.

Unfortunately, there were a few bugs in how this attribute was implemented.

I checked in a fix to the swift-3.0-branch today: https://github.com/apple/swift/commit/c1214fea45f0cfa58a5eb4ffc44ee0533f5c8cbe <https://github.com/apple/swift/commit/c1214fea45f0cfa58a5eb4ffc44ee0533f5c8cbe>

After the above patch, it will no longer make a difference if the function type is written directly (as in doManualClosure) or a typealias (a in doClosure). In both cases, the closure should be non-escaping, unless explicitly declared @escaping. However in beta 6 you see the bug where the closure in doClosure() is escaping, even though no explicit @escaping attribute was specified, because it was written with a typealias.

If you have time, please test the next snapshot when it is released, or build Swift from swift-3.0-branch (or master) today, to see if it behaves as you expect.

Sorry for the confusion.

Slava

> On Aug 19, 2016, at 5:27 PM, Jon Shier via swift-users <swift-users at swift.org> wrote:
> 
> Another general question I have is how the self requirement in general has changed. I’m noticing several instances where my previous @noescape closures, which of course had that attribute removed, are now requiring self when they didn’t before and aren’t marked @escaping either. So I guess my question is, should there ever be an instance where a closure not marked @escaping requires the use of self?
> 
> 
> Jon
> 
>> On Aug 19, 2016, at 5:46 PM, Jon Shier <jon at jonshier.com> wrote:
>> 
>> Users:
>> 	I’m updating more code to beta 6 and have noticed a strange difference when calling functions with closure parameters where that closure is declared with a typealias. Take this class:
>> 
>> typealias Closure = () -> Void
>> 
>> class Thing {
>>   var array: [String] = []
>> 
>>   func doClosure(closure: Closure) {
>>       array.append("closure")
>>   }
>> 
>>   func doManualClosure(manualClosure: () -> Void) {
>>       array.append("manualClosure")
>>   }
>> 
>>   func append() {
>>       doClosure {
>>           doClosure {
>> 
>>           }
>>       }
>>   }
>> 
>>   func appendManual() {
>>       doManualClosure {
>>           doManualClosure {
>> 
>>           }
>>       }
>>   }
>> }
>> 
>> There’s an error triggered by the doClosure call inside a doClosure call saying that I need an explicit self capture. However, the same pattern in appendManual() builds just fine. I’m guessing this is a bug?
>> 
>> 
>> 
>> Jon
> 
> _______________________________________________
> swift-users mailing list
> swift-users at swift.org
> https://lists.swift.org/mailman/listinfo/swift-users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-users/attachments/20160819/70397d4e/attachment.html>