ManagedAtomic[LazyReference]: Always access ivar through pointer

The deinit implementations used to access the ivar directly, but that can confuse the compiler into assuming the value never changes after its initialization, because it doesn’t see accesses that are done via the pointer.

Stop accessing the ivar directly once it has been initialized.

Author: lorentey

Sources/Atomics/AtomicLazyReference.swift.gyb

@@ -139,6 +139,10 @@ public class ManagedAtomicLazyReference<Instance: AnyObject> {
   @usableFromInline
   internal typealias _Rep = Optional<Unmanaged<Instance>>.AtomicRepresentation
 
+  /// The atomic representation of the value stored inside.
+  ///
+  /// Warning: This ivar must only ever be accessed via `_ptr` after
+  /// its initialization.
   @usableFromInline
   internal let _storage: _Rep
 
@@ -149,7 +153,7 @@ public class ManagedAtomicLazyReference<Instance: AnyObject> {
   }
 
   deinit {
-    if let unmanaged = _storage.dispose() {
+    if let unmanaged = _ptr.pointee.dispose() {
       unmanaged.release()
     }
   }

Sources/Atomics/HighLevelTypes.swift.gyb

@@ -97,6 +97,10 @@ where Value.AtomicRepresentation.Value == Value {
   @usableFromInline
   internal typealias _Storage = Value.AtomicRepresentation
 
+  /// The atomic representation of the value stored inside.
+  ///
+  /// Warning: This ivar must only ever be accessed via `_ptr` after
+  /// its initialization.
   @usableFromInline
   internal var _storage: _Storage
 
@@ -108,7 +112,7 @@ where Value.AtomicRepresentation.Value == Value {
   }
 
   deinit {
-    _ = _storage.dispose()
+    _ = _ptr.pointee.dispose()
   }
 
   @_alwaysEmitIntoClient @inline(__always)

Sources/Atomics/autogenerated/AtomicLazyReference.swift

@@ -142,6 +142,10 @@ public class ManagedAtomicLazyReference<Instance: AnyObject> {
   @usableFromInline
   internal typealias _Rep = Optional<Unmanaged<Instance>>.AtomicRepresentation
 
+  /// The atomic representation of the value stored inside.
+  ///
+  /// Warning: This ivar must only ever be accessed via `_ptr` after
+  /// its initialization.
   @usableFromInline
   internal let _storage: _Rep
 
@@ -152,7 +156,7 @@ public class ManagedAtomicLazyReference<Instance: AnyObject> {
   }
 
   deinit {
-    if let unmanaged = _storage.dispose() {
+    if let unmanaged = _ptr.pointee.dispose() {
       unmanaged.release()
     }
   }

Sources/Atomics/autogenerated/HighLevelTypes.swift

@@ -99,6 +99,10 @@ where Value.AtomicRepresentation.Value == Value {
   @usableFromInline
   internal typealias _Storage = Value.AtomicRepresentation
 
+  /// The atomic representation of the value stored inside.
+  ///
+  /// Warning: This ivar must only ever be accessed via `_ptr` after
+  /// its initialization.
   @usableFromInline
   internal var _storage: _Storage
 
@@ -110,7 +114,7 @@ where Value.AtomicRepresentation.Value == Value {
   }
 
   deinit {
-    _ = _storage.dispose()
+    _ = _ptr.pointee.dispose()
   }
 
   @_alwaysEmitIntoClient @inline(__always)

Tests/AtomicsTests/AtomicLazyReference.swift

@@ -15,12 +15,17 @@ import Atomics
 
 class AtomicLazyReferenceTests: XCTestCase {
   func test_unsafe_create_destroy() {
+    XCTAssertEqual(LifetimeTracked.instances, 0)
     let v = UnsafeAtomicLazyReference<LifetimeTracked>.create()
-    defer { v.destroy() }
+    defer {
+      v.destroy()
+      XCTAssertEqual(LifetimeTracked.instances, 0)
+    }
     XCTAssertNil(v.load())
   }
 
   func test_unsafe_storeIfNilThenLoad() {
+    XCTAssertEqual(LifetimeTracked.instances, 0)
     do {
       let v = UnsafeAtomicLazyReference<LifetimeTracked>.create()
       XCTAssertNil(v.load())
@@ -39,6 +44,7 @@ class AtomicLazyReferenceTests: XCTestCase {
   }
 
   func test_managed_storeIfNilThenLoad() {
+    XCTAssertEqual(LifetimeTracked.instances, 0)
     do {
       let v = ManagedAtomicLazyReference<LifetimeTracked>()
       XCTAssertNil(v.load())