[SR-14564] "\(Self.self)" causes issue on Xcode 12.5 when Swift is optimized

[swift-ci]

Previous ID	SR-14564
Radar	rdar://problem/77465728
Original Reporter	matteolongeri_ovolab (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	1
Component/s	Compiler, SwiftSyntax
Labels	Bug
Assignee	None
Priority	Medium

md5: 4cc049e4929f10d973d6a2409610d84f

Issue Description:

Using Xcode 12.5 I have identified an issue with this instruction "(Self.self)" when it runs on a build created setting SWIFT_OPTIMIZATION_LEVEL to -O (Optimize for speed).

The instruction above is executed in a superclass (subclass of UIView) when it to load a NIB:

Bundle.main.loadNibNamed("\(Self.self)", owner: self, options: nil)

Instead of getting the right subclass name, it simply returns "Self" and this generate the following error:

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Could not load NIB in bundle: '...' with name 'Self''

This never happens before with previous versions of Xcode, and it still does not happen when the build is generate without using optimization -Onone.

To fix it I have changed "(Self.self)" with "(type(of: self))". This way it works, but I think that it should be investigate why the original version causes that kind of issue when Swift is optimized.

Forcing optimization in Debug, I was able to reproduce the issue. I have also tried to insert a breakpoint before the crash, trying to execute the instruction in Console with po command, but it works as expected, printing the right class name.

[swift-ci]

Comment by Matteo Longeri (JIRA)

UPDATE: To be sure that this issue is directly related to Xcode 12.5 I have created a simple project, defining:

class MyClass {

    var classname: String {
        "\(Self.self)"
    }

}

and calling it from the ViewController:

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.

        let c = MyClass()
        print(c.classname)
    }

}

When I activate -O optimization in Debug, the Console prints: Self.

Just to confirm that this issue is not directly related to the app I am working on, but it is reproducible in any context.

Matteo

[typesanitizer]

@swift-ci create

[eeckstein]

Thanks for reporting. This is already fixed in Swift 5.5: apple/swift#36717

[swift-ci]

Comment by Matteo Longeri (JIRA)

Thanks for your answer @eeckstein!

Best regards,

Matteo

[swift-ci]

Comment by Andrey Yakushev (JIRA)

Issue appears only in classes. It's fine to write

"\(Self.self)"

inside structs.