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[SR-2355] Typealias and escaping #44962

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swift-ci opened this issue Aug 16, 2016 · 3 comments
Closed

[SR-2355] Typealias and escaping #44962

swift-ci opened this issue Aug 16, 2016 · 3 comments
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@slavapestov
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself

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@swift-ci
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Previous ID SR-2355
Radar None
Original Reporter diegosanchezr (JIRA User)
Type Bug
Status Resolved
Resolution Duplicate
Environment

Swift 3 Xcode 8 b6

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug
Assignee @slavapestov
Priority Medium

md5: 67bc4caa824a17d9c863a46912ed30bc

duplicates:

Issue Description:

Xcode b6:

typealias Completion = () -> Void

func myFunc(completion: Completion) {
    DispatchQueue.main.async {
        completion()
    }
}

myFunc {
    print("foo")
}

That seems to assume already that the closures scapes the function, while without the typealias I have to write

func myFunc(completion: @escaping () -> Void) {
    DispatchQueue.main.async {
        completion()
    }
}

I would like to write

func myFunc(completion: @escaping Completion) {
    DispatchQueue.main.async {
        completion()
    }
}

but that triggers the error "@escaping attribute applies only to function types"

Also, I see this syntax is supported:

typealias Completion = @escaping () -> Void

but it breaks quick lookup in Xcode (IMO @escaping shouldn't be allowed in typealias)
@nikolaykasyanov
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I'm experiencing a similar issue in Xcode 10.2 beta, the following code doesn't compile:

public enum Outcome {
    case A
    case B
}


public protocol Runner {
    typealias Completion = (Outcome) -> ()


    func run<D>(input: D, completion: @escaping Completion)
}

It does compile if run function isn't generic though.

Should I report it separately?

@slavapestov
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Yes please, this looks like a separate bug.

@nikolaykasyanov
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@slavapestov sure: SR-9760.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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@slavapestov slavapestov

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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself
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@slavapestov @nikolaykasyanov @swift-ci