NSTextStorageDeinitInSubclassProblme.swift

// Demos odditly in NSTextStorage subclass deinit.
//
// 1. Profile app in Allocations Instrument
// 2. Notice that after starting app 3 instances of MyTextStorage remain ... even though MyTextStorage.deinit is getting called.
// 3. Comment out the `let _ = self` line and the problem goes away.
// 4. I only notice this problem in subclasses of NSTextStorage, generally `let _ = self` seems fine in an deinit
//
class MyTextStorage: NSTextStorage {

    override init() {
        super.init()
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    required init?(pasteboardPropertyList propertyList: AnyObject, ofType type: String) {
        fatalError("init(pasteboardPropertyList:ofType:) has not been implemented")
    }

    deinit {
        // Comment this line out and problem goes away.
        let _ = self
    }
    
}

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {
    
    func applicationDidFinishLaunching(aNotification: NSNotification) {
        let _ = MyTextStorage()
        let _ = MyTextStorage()
        let _ = MyTextStorage()
    }
    
}