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

[Shawn Erickson]

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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