[stdlib] Set, Dictionary: Hide Cocoa index storage classes

Replace the single typed storage reference with two _BridgeObjects; this should give us plenty of space to play around with alternative representations.

Author: lorentey

stdlib/public/core/DictionaryBridging.swift

@@ -487,7 +487,8 @@ extension _CocoaDictionary: _DictionaryBuffer {
   internal func formIndex(after index: inout Index) {
     validate(index)
     let isUnique = index.isUniquelyReferenced()
-    if !isUnique { index.storage = index.copy() }
+    if !isUnique { index = index.copy() }
+    _sanityCheck(index.isUniquelyReferenced())
     let storage = index.storage // FIXME: rdar://problem/44863751
     storage.currentKeyIndex += 1
   }
@@ -575,17 +576,34 @@ extension _CocoaDictionary {
   @usableFromInline
   internal struct Index {
     @usableFromInline
-    internal var storage: Storage
+    internal var _object: Builtin.BridgeObject
+    @usableFromInline
+    internal var _storage: Builtin.BridgeObject
+
+    internal var object: AnyObject {
+      @inline(__always)
+      get {
+        return _bridgeObject(toNonTaggedObjC: _object)
+      }
+    }
+
+    internal var storage: Storage {
+      @inline(__always)
+      get {
+        let storage = _bridgeObject(toNative: _storage)
+        return unsafeDowncast(storage, to: Storage.self)
+      }
+    }
 
     internal init(_ storage: Storage) {
-      self.storage = storage
+      self._object = _bridgeObject(fromNonTaggedObjC: storage.base.object)
+      self._storage = _bridgeObject(fromNative: storage)
     }
   }
 }
 
 extension _CocoaDictionary.Index {
   // FIXME(cocoa-index): Try using an NSEnumerator to speed this up.
-  @usableFromInline
   internal class Storage {
   // Assumption: we rely on NSDictionary.getObjects when being
     // repeatedly called on the same NSDictionary, returning items in the same
@@ -620,13 +638,21 @@ extension _CocoaDictionary.Index {
 extension _CocoaDictionary.Index {
   @inlinable
   internal mutating func isUniquelyReferenced() -> Bool {
+    defer { _fixLifetime(self) }
+    guard _isNativePointer(_storage) else {
+      return false
+    }
+    unowned(unsafe) var storage = _bridgeObject(toNative: _storage)
     return _isUnique_native(&storage)
   }
 
   @usableFromInline
-  internal mutating func copy() -> Storage {
+  internal mutating func copy() -> _CocoaDictionary.Index {
     let storage = self.storage
-    return Storage(storage.base, storage.allKeys, storage.currentKeyIndex)
+    return _CocoaDictionary.Index(Storage(
+        storage.base,
+        storage.allKeys,
+        storage.currentKeyIndex))
   }
 }
 
@@ -647,7 +673,7 @@ extension _CocoaDictionary.Index {
   internal var age: Int32 {
     @_effects(readonly)
     get {
-      return _HashTable.age(for: storage.base.object)
+      return _HashTable.age(for: object)
     }
   }
 }

stdlib/public/core/SetBridging.swift

@@ -362,7 +362,7 @@ extension _CocoaSet: _SetBuffer {
   internal func formIndex(after index: inout Index) {
     validate(index)
     let isUnique = index.isUniquelyReferenced()
-    if !isUnique { index.storage = index.copy() }
+    if !isUnique { index = index.copy() }
     let storage = index.storage // FIXME: rdar://problem/44863751
     storage.currentKeyIndex += 1
   }
@@ -412,17 +412,34 @@ extension _CocoaSet {
   @usableFromInline
   internal struct Index {
     @usableFromInline
-    internal var storage: Storage
+    internal var _object: Builtin.BridgeObject
+    @usableFromInline
+    internal var _storage: Builtin.BridgeObject
+
+    internal var object: AnyObject {
+      @inline(__always)
+      get {
+        return _bridgeObject(toNonTaggedObjC: _object)
+      }
+    }
+
+    internal var storage: Storage {
+      @inline(__always)
+      get {
+        let storage = _bridgeObject(toNative: _storage)
+        return unsafeDowncast(storage, to: Storage.self)
+      }
+    }
 
     internal init(_ storage: __owned Storage) {
-      self.storage = storage
+      self._object = _bridgeObject(fromNonTaggedObjC: storage.base.object)
+      self._storage = _bridgeObject(fromNative: storage)
     }
   }
 }
 
 extension _CocoaSet.Index {
   // FIXME(cocoa-index): Try using an NSEnumerator to speed this up.
-  @usableFromInline
   internal class Storage {
     // Assumption: we rely on NSDictionary.getObjects when being
     // repeatedly called on the same NSDictionary, returning items in the same
@@ -457,13 +474,21 @@ extension _CocoaSet.Index {
 extension _CocoaSet.Index {
   @inlinable
   internal mutating func isUniquelyReferenced() -> Bool {
+    defer { _fixLifetime(self) }
+    guard _isNativePointer(_storage) else {
+      return false
+    }
+    unowned(unsafe) var storage = _bridgeObject(toNative: _storage)
     return _isUnique_native(&storage)
   }
 
   @usableFromInline
-  internal mutating func copy() -> Storage {
+  internal mutating func copy() -> _CocoaSet.Index {
     let storage = self.storage
-    return Storage(storage.base, storage.allKeys, storage.currentKeyIndex)
+    return _CocoaSet.Index(Storage(
+        storage.base,
+        storage.allKeys,
+        storage.currentKeyIndex))
   }
 }
 
@@ -484,7 +509,7 @@ extension _CocoaSet.Index {
   internal var age: Int32 {
     @_effects(releasenone)
     get {
-      return _HashTable.age(for: storage.base.object)
+      return _HashTable.age(for: object)
     }
   }
 }