Swift Interpolated String memory leak

AppDelegate.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?


    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        
        // Instruments shows a memory leak here
        print("The number of the counting shall be \(3)")
        
        // but not here
        //print("The number of the counting shall be " + 3.description)
        
        if let widget = store.value.currentWidget {
            print(widget.widgetID)
        }

        return true
    }
}

Models.swift

import Foundation

struct Doodad {
    var doodadID: String
    var name: String
}

struct Widget {
    var widgetID: String
    var doodad: Doodad
    var startDate: NSDate
    var endDate: NSDate?
    var prop1: String?
    var prop2: String?
    var prop3: [String]
    var prop4: [String]
    var prop5: [String]
    var prop6: Double
    var prop7: NSDate?
}

enum NavigationState {
    case Main
    case Compare(Widget, Widget)
}

struct AppState {
    var navigationState: NavigationState = .Main
    var widgets = [Widget]()
    var prop1: [String] = []
    var prop2: String?
    
    init(widget: Widget) {
        widgets = [widget]
    }
    
    var currentWidget: Widget? {
        return widgets.filter { $0.endDate == nil }
            .sort { $0.0.startDate.compare($0.1.startDate) == .OrderedDescending }
            .first
    }
}

class Store<T> {
    var value: T
    
    init(_ initial: T) {
        value = initial
    }
}

let widget = Widget(widgetID: "sdfg", doodad: Doodad(doodadID: "8765", name: "jhg"), startDate: NSDate(), endDate: nil, prop1: nil, prop2: nil, prop3: [], prop4: [], prop5: [] , prop6: 10, prop7: nil)

let appState = AppState(widget: widget)
let store = Store<AppState>(appState)

I suffered from NSZombies when interpolating as well. Didn't check leaks, though. Maybe related?
https://gist.github.com/DivineDominion/c069c8d3d38d7cb880b5354524acf579

http://openradar.appspot.com/26349281