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[SR-3055] Switch statements fail to test optionals for equality #45645

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swift-ci opened this issue Oct 27, 2016 · 3 comments
Closed

[SR-3055] Switch statements fail to test optionals for equality #45645

swift-ci opened this issue Oct 27, 2016 · 3 comments
Labels
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-3055
Radar None
Original Reporter bogidon (JIRA User)
Type Bug
Status Resolved
Resolution Done
Environment

Xcode 8.0
OS X 10.11.6

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug
Assignee None
Priority Medium

md5: 81813b398f05d32291bc44dcd426803c

relates to:

  • SR-1535 No == overload exists for comparing optional arrays.

Issue Description:

1. If the switch statement's "value to be considered" is an optional and is being equated to other optionals, Swift will bridge the "value to be considered" to a _OptionalNilComparisonType, which cannot be equated to an optional of the same type.

let pet: String? = "dog"
let dog: String? = "dog"
let cat: String? = nil

// Does not work
switch pet {
case dog:
    print(dog)
    
case cat:
    print(cat)
    
default:
    print("did not match")
}

// Does work
switch () {
case _ where pet == dog:
    print(dog)
    
case _ where pet == cat:
    print(cat)
    
default:
    print("did not match")
}

2. If the switch statement's "value to be considered" is not an optional but is being equated to optionals, the act of equating fails.

let pet: String = "dog"
let dog: String? = "dog"
let cat: String? = nil

// Does not work
switch pet {
case dog:
    print(dog)
    
case cat:
    print(cat)
    
default:
    print("did not match")
}

// Does work
switch () {
case _ where pet == dog:
    print(dog)
    
case _ where pet == cat:
    print(cat)
    
default:
    print("did not match")
}

This is my first time posting here, I'm sorry if the formatting is off.
@belkadan
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The first problem should go away with conditional conformances, which will allow Optional to be Equatable when its element type is Equatable. The second one is correct behavior, I think, but at that point you'd be able to convert to the first by explicitly coercing to Optional in the argument to switch.

@Dante-Broggi
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@belkadan, your comment implies something should happen to this report now that SE-0143 (Conditional Conformances) was implemented (in Swift 4.2)?

@belkadan
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Yep, both examples now pass, so we can call this done.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself
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@belkadan @swift-ci @Dante-Broggi