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[SR-9760] Can't add @escaping to an argument of generic function having typealiased function type #52188

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nikolaykasyanov opened this issue Jan 25, 2019 · 9 comments
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[SR-9760] Can't add @escaping to an argument of generic function having typealiased function type #52188

nikolaykasyanov opened this issue Jan 25, 2019 · 9 comments
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@theblixguy
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself regression swift 5.0

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@nikolaykasyanov
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Previous ID SR-9760
Radar rdar://problem/47550733
Original Reporter @nikolaykasyanov
Type Bug
Status Resolved
Resolution Done
Environment

Xcode 10.2 beta (10P82s)

Apple Swift version 5.0 (swiftlang-1001.0.45.7 clang-1001.0.37.7)

Target: x86_64-apple-darwin18.2.0

ABI version: 0.6

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, 5.0Regression
Assignee @theblixguy
Priority Medium

md5: d7be05a7d980928bf2303b1dee8fe3ed

is duplicated by:

Issue Description:

This code snippet doesn't compile in Swift 5:

public enum Outcome {
    case A
    case B
}

public protocol Runner {
    typealias Completion = (Outcome) -> ()
    func run<D>(input: D, completion: @escaping Completion)
}
error: @escaping attribute only applies to function types
    func run<D>(input: D, completion: @escaping Completion)
                                      ~^~~~~~~~~~~~~~~~~~

It compiles if function isn't generic though.
@slavapestov
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Thanks, this is definitely a regression. It works for non-generic protocol requirements, and generic functions inside non-protocols. Only generic functions in protocols are busted. I think I know why...

@belkadan
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@theblixguy, did your recent fix cover this?

@belkadan
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Oh, I didn't realize this was a regression at first. Thanks for the report, Nikolay!

@slavapestov
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The problem is that protocol type aliases are resolved as DependentMemberType in the structural stage of type resolution. We need to ignore attributes in this stage instead of diagnosing them.

@theblixguy
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Fixed on master and Swift 5.0 branch.

@nikolaykasyanov
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Thank you!

@nikolaykasyanov
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May I ask how long it usually takes for a fix to land in Xcode beta? Beta 3 doesn't have this fix.

@theblixguy
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This should be available in the next beta or the final release (whichever comes next).

@nikolaykasyanov
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@theblixguy thank you.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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@theblixguy theblixguy

Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself regression swift 5.0
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@slavapestov @nikolaykasyanov @belkadan @theblixguy @AnthonyLatsis