A Playground that demos a bug where a cast using `as` causes a, "fatal error: can't unsafeBitCast between types of different sizes".

SwiftCastingBug.swift

//: Playground - Demos a bug where a cast using `as` causes a, "fatal error: can't unsafeBitCast between types of different sizes"

import UIKit

protocol Thingable {
    func getStuff()
}

enum MyList: Thingable {
    case One
    case Two
    
    func getStuff() {
        print("BOOM!")
    }
}

class MyClass<T: Thingable> {
    
    lazy var things: [Thingable]? = nil
}

class MyConcreateClass: MyClass<MyList> {
    
    override init() {
        
        super.init()
        
        /*** Because `things` is of type `T: Thingable` adding MyList objects worksa as expected, 
         however truing to cast using `self.things as? [MyList]` fails with the error
         "fatal error: can't unsafeBitCast between types of different sizes" ***/
        self.things = [MyList.One, MyList.One, MyList.Two, MyList.Two]
    }
    
    func doCast() -> [MyList]?  {
        
        var temp1 : [MyList] = []
        
        for item in self.things! {
            
            /*** Reports its type as MyList ***/
            //print("ITEM: \(item.dynamicType) -> \(item)")
            
            /*** This gives the error
            Playground execution failed: MyPlayground.playground:35:26: error: cannot convert value of type 'Thingable' to expected argument type 'MyList' ***/
            //temp1.append(item)
            
            /*** This works!? ***/
            temp1.append(item as! MyList)
        }
        
        /*** Also fails with: fatal error: can't unsafeBitCast between types of different sizes ***/
        //if self.things is [MyList] {
        //    //wont work!
        //}
        
        /*** This fails: fatal error: can't unsafeBitCast between types of different sizes ***/
        //let temp = self.things as? [MyList]
        
        /*** flatMap() is a workaround ***/
        return self.things?.flatMap { $0 as? MyList }
        
        /*** fails ***/
        //return self.things as [MyList]
        
        //return temp1
    }
}

class Wrapper: NSObject {
    lazy var concreate: MyConcreateClass = MyConcreateClass()
}

let stone = Wrapper()
let objects = stone.concreate.doCast()

print("Objects: \(objects!)")