Casting from type Any to AnyObject always fails when Any contains an optional

gistfile1.swift

//: Playground - noun: a place where people can play
import UIKit

var arr = [Any]();
var optionalString: String? = "foo";
arr.append(optionalString);
print(arr[0]);   // "Optional("foo")\n"

if let optionalValue = arr[0] as? AnyObject{
    print("success")  // never executed...
}
else {
    print("fail")   // "fail"
}