add some type checking

Author: lhoward

Foundation/NSKeyedArchiver.swift

@@ -20,6 +20,10 @@ internal let NSKeyedArchivePlistVersion = 100000
 internal let NSKeyedArchiverSystemVersion : UInt32 = 2000
 
 internal func objectRefGetValue(objectRef : CFKeyedArchiverUID) -> UInt32 {
+    if objectRef.dynamicType != __NSCFType.self ||
+        CFGetTypeID(objectRef) != _CFKeyedArchiverUIDGetTypeID() {
+        fatalError("Object \(objectRef) is not a CFKeyedArchiverUID")
+    }
     return _CFKeyedArchiverUIDGetValue(unsafeBitCast(objectRef, CFKeyedArchiverUIDRef.self))
 }
 internal var NSPropertyListClasses : [AnyClass] = [

Foundation/NSKeyedUnarchiver.swift

@@ -355,7 +355,7 @@ public class NSKeyedUnarchiver : NSCoder {
         Returns true if objectOrReference represents a reference to another object in the archive
      */
     internal class func _isReference(objectOrReference : Any?) -> Bool {
-        if let cf = objectOrReference as? AnyObject {
+        if let cf = objectOrReference as? __NSCFType {
             return CFGetTypeID(cf) == _CFKeyedArchiverUIDGetTypeID()
         } else {
             return false