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[SR-8125] Swift 4.2 exhaustivity checker regression #50657

sharplet opened this issue Jun 27, 2018 · 5 comments

[SR-8125] Swift 4.2 exhaustivity checker regression #50657

sharplet opened this issue Jun 27, 2018 · 5 comments


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@sharplet sharplet commented Jun 27, 2018

Previous ID SR-8125
Radar rdar://problem/41525746
Original Reporter @sharplet
Type Bug
Status Closed
Resolution Done

Xcode Version 10.0 beta 2 (10L177m)

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, 4.2Regression
Assignee @belkadan
Priority Medium

md5: 151824427e3aec5ee74b46aec98a0730

is duplicated by:

  • SR-8197 REGRESSION: Switch exhaustiveness handles Never separately from other no-valued types

Issue Description:

The following code compiles in Swift 4.1, but fails with an exhaustivity error in Swift 4.2:

extension Signal where Value: ResultProtocol, Error == NoError {
    func dematerializeResults() -> Signal<Value.Value, Value.Error> {
        return .init { observer, lifetime in
            lifetime += self.observe { event in
                switch event {
                case let .value(value):
                        ifSuccess: { value in
                            observer.send(value: value)
                        }, ifFailure: { error in
                            observer.send(error: error)
                case .completed:
                case .interrupted:

The Event enum has a failure case which in this case has an associated value of type NoError, and thus is impossible to construct.

Reproduced on this branch in the ReactiveSwift repository:

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@belkadan belkadan commented Jun 27, 2018

I wonder if this is fallout from unknown case.

@swift-ci create

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@belkadan belkadan commented Jul 2, 2018

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@belkadan belkadan commented Jul 3, 2018

4.2: #17690

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@AnnaZaks AnnaZaks mannequin commented Aug 4, 2018

@sharplet, Could you verify if the problem is fixed and if so move the JIRA to "Closed"?

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@sharplet sharplet commented Aug 19, 2018

This compiled for me on the latest Xcode beta, thanks!

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