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[SR-6353] Cast from to unrelated type always fails but doesn't fail #48903

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swift-ci opened this issue Nov 10, 2017 · 1 comment
Closed

[SR-6353] Cast from to unrelated type always fails but doesn't fail #48903

swift-ci opened this issue Nov 10, 2017 · 1 comment
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself type checker Area → compiler: Semantic analysis

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@swift-ci
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Previous ID SR-6353
Radar rdar://problem/35469176
Original Reporter Sylvain (JIRA User)
Type Bug
Status Resolved
Resolution Duplicate

Attachment: Download

Environment

Xcode 9.1, Swift 4.0

Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Bug, TypeChecker
Assignee None
Priority Medium

md5: 40e13a864e7b03441494cf14b00df9c1

duplicates:

  • SR-5252 Warning: Cast from … to unrelated type false positive?

is duplicated by:

  • SR-6771 "Cast always fails" false positive warning when casting to a generic subclass

Issue Description:

Trying to cast a UITableViewCell inherited class containing a generic shows a warning that casting from UITableViewCell back to this class will always fail when it doesn't.

Better open the Playground to understand the problem.
@belkadan
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class SharedSuperClass { }
protocol MyProtocol { }
class MyView: SharedSuperClass, MyProtocol { }
class MyGenericClass<View: MyProtocol>: SharedSuperClass { }

class ThisWarningLies<View: SharedSuperClass & MyProtocol> {
 func doStuff() {
     let cell: SharedSuperClass = MyGenericClass<View>()
     if cell is MyGenericClass<View> {
         print("Never say never")
     }
 }
}

ThisWarningLies<MyView>().doStuff()

Might be the same as something else we have, might not. Thanks for the report!

@swift-ci create

@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 type checker Area → compiler: Semantic analysis
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@belkadan @swift-ci