[SR-8026] ObjC convenience initializers leak stored properties

[dmcyk]

Previous ID	SR-8026
Radar	None
Original Reporter	@dmcyk
Type	Bug
Status	Resolved
Resolution	Invalid

Attachment: Download

Environment

Xcode 10.0 beta (10L176w)
macOS 10.14 Beta (18A293u)
Swift 4.2

Additional Detail from JIRA

Votes	0
Component/s
Labels	Bug
Assignee	None
Priority	Medium

md5: bbb8f81c61679f46fa506d5e6bd59bae

Issue Description:

Given Objective-C class with following initializers:

-(id _Nonnull)initWithValue:(NSString* _Nonnull)value;
-(id _Nonnull)initConvenienceWithValue:(NSString* _Nonnull)value;

Where `initConvenienceWithValue:` calls to the designated initializer `initWithValue:`.

When such class is subclassed in Swift, both initializers must be overridden. e.g.

class Child: LeakObject {

    let context: Context = {
        return Context()
    }()

    override init(convenienceWithValue value: String) {
        super.init(convenienceWithValue: value)
    }

    override init(value: String) {
        super.init(value: value)
    }
}

When the convenience initializer is called from Swift, there will be one leaked instance of `Context` object, as it will be allocated twice during Swift 'convenience' initializer call and later when Objective-C calls to its designated initializer.

[dmcyk]

Note: marking property `lazy var` instead solves the problem can be a temporary solution.

[belkadan]

If you want to make an Objective-C class subclassable from Swift, you have to annotate the designated initializer(s) with NS_DESIGNATED_INITIALIZER. Then the other one will be properly treated as a convenience initializer.

[dmcyk]

oh okay, I wasn't aware of that.
I found that trying to subclass UINavigationController, will report it to rdar.
Thank you

[belkadan]

Yikes! Yes, thanks for the Radar.