[SR-9036] Passing a dictionary as parameter of initializer of ObjC class in Swift, yields "null" value

[swift-ci]

Previous ID	SR-9036
Radar	rdar://problem/45962521
Original Reporter	petar.belokonski (JIRA User)
Type	Bug

Attachment: Download

Environment

SwiftObjCPlay.zip

Additional Detail from JIRA

Votes	0
Component/s
Labels	Bug, 4.2Regression
Assignee	None
Priority	Medium

md5: 05dc781faf00fc6c7a8030c7994f7a76

Issue Description:

Weird situation I've stumbled upon once upgrading to XCode 10.

I have an ObjectiveC class which I initialize in Swift. The initializer accepts NSDictionary as a parameter. If I pass in the dictionary directly into the initializer like so:

let car = Car(parts: [myKey : myValue])

Then, back in ObjC world, when printing the contents of the dictionary it shows the value as "(null)".

Everything works fine if I do:

let parts = [myKey : myValue]
let car = Car(parts: parts)

This issue exists on any version of Swift on XCode 10. The issue doesn't exist on XCode 9.

I am attaching a sample project where this is illustrated.

[belkadan]

Reproduced. Very strange; what Petar didn't mention was that when the dictionary is bridged back to Swift, the value is there.

@swift-ci create

[belkadan]

The difference between the two invocations is whether we create a [String?: String] dictionary and convert it to [AnyHashable: Any], or whether we just start with [AnyHashable: Any] from the beginning. But they should indeed have the same observable behavior.

[lorentey]

This is because Optional doesn't currently have a custom AnyHashable representation, making it incompatible with its wrapped values when converted to AnyHashable.

Adding such a representation is tracked in https://bugs.swift.org/browse/SR-9047, following the forum discussion at https://forums.swift.org/t/xcode-10-swift-objc-dictionary-compatibility/17148.