[SR-1146] Enum with single case crashes when referenced as class property within initializer

[swift-ci]

Previous ID	SR-1146
Radar	None
Original Reporter	flobraunschweig (JIRA User)
Type	Bug
Status	Reopened
Resolution

Attachment: Download

Environment

Xcode 7.3, Swift 2.2

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, RunTimeCrash
Assignee	None
Priority	Medium

md5: b8a7dc0da5ceb86328da85d2daa4165f

Issue Description:

When using the following notation, the application crashes at runtime with a bad access exception:

App Delegate:

let a = EnumCrashTest()  // Runtime crash with bad access exception here!

A Class Definition:

enum SingleCaseEnum {
    case FirstCase
}
class EnumCrashTest {
    var singleCaseEnum: SingleCaseEnum
    
    init() {
        singleCaseEnum = .FirstCase
    }
}

The bug does not occur when using a struct instead of a class or if more than one cases are defined in the enumeration.

[belkadan]

@jckarter, is this the same thing you were looking at earlier?

[jckarter]

Yeah, this should be fixed:

#1914 (2.2)
#1921 (master)

[swift-ci]

Comment by Sergej Jaskiewicz (JIRA)

Actually, I've just expirienced this very bug after I migrated to Swift 3. As soon as I added one more case to an enum, it was gone.

I couldn't reproduce it in a Playground.

[belkadan]

Sergej, can you attach the project where it reproduces?

[swift-ci]

Comment by Sergej Jaskiewicz (JIRA)

Yep. You can reproduce it by running a test method `test_ThatKeyTypeButtons_passTheirLabelTextToOutput`. Run on iOS 10.

GroupLockiOS.zip

[jckarter]

This looks like a different problem. You don't need the empty enum, just the empty struct, in a nested class. Here's a smaller repro:

class Outer {
  class Foo {
    var zim = Bar()
    var bas = Outer()
  }
}

struct Bar { }

_ = Outer.Foo()

[jckarter]

broadway_lamb (JIRA User) Testing a fix: #4452

In the meantime, you can try de-nesting the type as a workaround, which should avoid the runtime bug. Thanks for catching this!

[swift-ci]

Comment by Sergej Jaskiewicz (JIRA)

Thank you. But, like I said, adding a second case to the enum solved the problem as well, or at least made it look like it was solved.

[jckarter]

Sure, making an empty type nonempty should work around it too. In case that's inconvenient, since you now need to switch that dummy case and things like that, you can also try denesting classes.