[swift-users] Swift 3 (Xcode 8 GM) issue with @escaping

[Shawn Erickson]

I see https://bugs.swift.org/browse/SR-2324 and
https://bugs.swift.org/browse/SR-2444 which looks related to this issue and
may explain the error I saw on "the other side" of this.



On Wed, Sep 7, 2016 at 3:28 PM Shawn Erickson <shawnce at gmail.com> wrote:

> Yeah I actually have a few of those myself that I can no longer do.
>
> On Wed, Sep 7, 2016 at 3:26 PM Jon Shier <jon at jonshier.com> wrote:
>
>> Perhaps relatedly, it no longer seems possible to mark typealiased
>> closures as @escaping. That was quite handy when you know that closures
>> will always be used asynchronously.
>>
>>
>> Jon
>>
>>
>> On Sep 7, 2016, at 6:15 PM, Shawn Erickson via swift-users <
>> swift-users at swift.org> wrote:
>>
>> I should note that this issue also appeared in an earlier variant of
>> Swift after the addition of @escaping but I was on vacation so didn't get a
>> chance to report it then. It isn't new with the Xcode 8 GM.
>>
>> On Wed, Sep 7, 2016 at 3:08 PM Shawn Erickson <shawnce at gmail.com> wrote:
>>
>>> I like and fully supported the change to @escaping away from @noescape
>>> however in a body of code that I am porting to the latest Swift 3 variant
>>> (as found in Xcode 8 GM) I am hitting an issue for methods that take an
>>> optional completion closure. If optional is involved I can't find a way to
>>> apply @escape to the escaping closure. See the following for an basic
>>> example...
>>>
>>> Is their a way to do what I need and/or is this an edge case in the
>>> implementation of @escaping?
>>>
>>> typealias MyCallback = (String)->()
>>>
>>> // Happy
>>> func foo1(bar: String, completion: ((String)->())) {
>>>     completion(bar)
>>> }
>>>
>>> // Happy
>>> func foo2(bar: String, completion: MyCallback) {
>>>     completion(bar)
>>> }
>>>
>>> // Happy
>>> func foo3(bar: String, completion: ((String)->())? = nil) {
>>>     completion?(bar)
>>> }
>>>
>>> // Happy
>>> func foo4(bar: String, completion: MyCallback? = nil) {
>>>     completion?(bar)
>>> }
>>>
>>> // Happy
>>> func foo5(bar: String, completion: Optional<MyCallback> = nil) {
>>>     completion?(bar)
>>> }
>>>
>>> // Happy
>>> func foo6(bar: String, completion: @escaping (String)->()) {
>>>     completion(bar)
>>> }
>>>
>>> // Happy
>>> func foo7(bar: String, completion: @escaping MyCallback) {
>>>     completion(bar)
>>> }
>>>
>>> // Unhappy...
>>> // "@escaping attribute only applies to function types"
>>> func foo8(bar: String, completion: @escaping ((String)->())? = nil) {
>>>     completion?(bar)
>>> }
>>>
>>> // Unhappy...
>>> // "@escaping attribute only applies to function types"
>>> func foo9(bar: String, completion: @escaping MyCallback? = nil) {
>>>     completion?(bar)
>>> }
>>>
>>> // Unhappy...
>>> // "@escaping attribute only applies to function types"
>>> func foo10(bar: String, completion: (@escaping ((String)->()))? = nil) {
>>>     completion?(bar)
>>> }
>>>
>>> // Unhappy...
>>> // "@escaping attribute only applies to function types"
>>> func foo11(bar: String, completion: (@escaping MyCallback)? = nil) {
>>>     completion?(bar)
>>> }
>>>
>>> // Unhappy...
>>> // "@escaping attribute only applies to function types"
>>> func foo12(bar: String, completion: Optional<@escaping MyCallback> =
>>> nil) {
>>>     completion?(bar)
>>> }
>>>
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