- Instrument _SwiftValue to understand values that can be returned by as AnyObject casts on Darwin, and move all code back to _SwiftValue.store/fetch.

Author: millenomi

Foundation/Bridging.swift

@@ -16,6 +16,16 @@ public protocol _StructBridgeable {
     func _bridgeToAny() -> Any
 }
 
+fileprivate protocol Unwrappable {
+    func unwrap() -> Any?
+}
+
+extension Optional: Unwrappable {
+    func unwrap() -> Any? {
+        return self
+    }
+}
+
 /// - Note: This does not exist currently on Darwin but it is the inverse correlation to the bridge types such that a 
 /// reference type can be converted via a callout to a conversion method.
 public protocol _StructTypeBridgeable : _StructBridgeable {
@@ -65,7 +75,12 @@ internal final class _SwiftValue : NSObject, NSCopying {
 
     static func fetch(_ object: AnyObject?) -> Any? {
         if let obj = object {
-            return fetch(nonOptional: obj)
+            let value = fetch(nonOptional: obj)
+            if let wrapper = value as? Unwrappable, wrapper.unwrap() == nil {
+                return nil
+            } else {
+                return value
+            }
         }
         return nil
     }
@@ -75,6 +90,8 @@ internal final class _SwiftValue : NSObject, NSCopying {
             return true
         } else if object === kCFBooleanFalse {
             return false
+        } else if type(of: object) == NSNull.self {
+            return Optional<Any>.none as Any
         } else if let container = object as? _SwiftValue {
             return container.value
         } else if let val = object as? _StructBridgeable {
@@ -84,6 +101,13 @@ internal final class _SwiftValue : NSObject, NSCopying {
         }
     }
 
+    static func store(optional value: Any?) -> NSObject? {
+        if let val = value {
+            return store(val)
+        }
+        return nil
+    }
+    
     static func store(_ value: Any?) -> NSObject? {
         if let val = value {
             return store(val)
@@ -94,8 +118,20 @@ internal final class _SwiftValue : NSObject, NSCopying {
     static func store(_ value: Any) -> NSObject {
         if let val = value as? NSObject {
             return val
+        } else if let opt = value as? Unwrappable, opt.unwrap() == nil {
+            return NSNull()
         } else {
-            return (value as AnyObject) as! NSObject
+            #if canImport(ObjectiveC)
+                // On Darwin, this can be a native (ObjC) _SwiftValue.
+                let boxed = (value as AnyObject)
+                if !(boxed is NSObject) {
+                    return _SwiftValue(value) // Do not emit native boxes — wrap them in Swift Foundation boxes instead.
+                } else {
+                    return boxed as! NSObject
+                }
+            #else
+                return (value as AnyObject) as! NSObject
+            #endif
         }
     }
 

Foundation/NSArray.swift

@@ -337,7 +337,7 @@ open class NSArray : NSObject, NSCopying, NSMutableCopying, NSSecureCoding, NSCo
             } else {
               let val1 = object(at: idx)
               let val2 = otherArray[idx]
-                if !((val1 as AnyObject) as! NSObject).isEqual(val2 as AnyObject) {
+                if !_SwiftValue.store(val1).isEqual(_SwiftValue.store(val2)) {
                     return false
                 }
             }

Foundation/NSDictionary.swift

@@ -396,9 +396,10 @@ open class NSDictionary : NSObject, NSCopying, NSMutableCopying, NSSecureCoding,
                     return false
                 }
             } else {
-              let otherBridgeable = otherDictionary[key as! AnyHashable]
-              let bridgeable = object(forKey: key)!
-                if !((otherBridgeable as AnyObject) as! NSObject).isEqual(bridgeable as AnyObject) {
+                let otherBridgeable = otherDictionary[key as! AnyHashable]
+                let bridgeable = object(forKey: key)!
+                let equal = _SwiftValue.store(optional: otherBridgeable)?.isEqual(_SwiftValue.store(bridgeable))
+                if equal != true {
                     return false
                 }
             }

Foundation/NSKeyedArchiver.swift

@@ -597,7 +597,7 @@ open class NSKeyedArchiver : NSCoder {
         object = _replacementObject(objv)
 
         // bridge value types
-        object = object as AnyObject
+        object = _SwiftValue.store(object)
 
         objectRef = _referenceObject(object, conditional: conditional)
         guard let unwrappedObjectRef = objectRef else {

Foundation/NSKeyedUnarchiver.swift

@@ -483,7 +483,7 @@ open class NSKeyedUnarchiver : NSCoder {
                 _cacheObject(object!, forReference: objectRef as! _NSKeyedArchiverUID)
             }
         } else {
-            object = dereferencedObject as AnyObject
+            object = _SwiftValue.store(dereferencedObject)
         }
 
         return _replacementObject(object)

Foundation/NSSet.swift

@@ -46,7 +46,7 @@ open class NSSet : NSObject, NSCopying, NSMutableCopying, NSSecureCoding, NSCodi
         super.init()
         let buffer = UnsafeBufferPointer(start: objects, count: cnt)
         for obj in buffer {
-            _storage.insert(obj as! NSObject)
+            _storage.insert(_SwiftValue.store(obj))
         }
     }