[Concurrency] Do not allow accessing actor-isolated superclass properties

from nonisolated subclass initializers.

Author: hborla

lib/Sema/TypeCheckConcurrency.cpp

@@ -1512,6 +1512,15 @@ static bool isStoredProperty(ValueDecl const *member) {
   return false;
 }
 
+static bool isNonInheritedStorage(ValueDecl const *member,
+                                  DeclContext const *useDC) {
+  auto *nominal = useDC->getParent()->getSelfNominalTypeDecl();
+  if (!nominal)
+    return false;
+
+  return isStoredProperty(member) && member->getDeclContext() == nominal;
+}
+
 /// Based on the former escaping-use restriction, which was replaced by
 /// flow-isolation. We need this to support backwards compatability in the
 /// type-checker for programs prior to Swift 6.
@@ -1727,7 +1736,7 @@ static bool checkedByFlowIsolation(DeclContext const *refCxt,
     return false;
 
   // Stored properties are definitely OK.
-  if (isStoredProperty(member))
+  if (isNonInheritedStorage(member, fnDecl))
     return true;
 
   return false;
@@ -5659,7 +5668,7 @@ ActorReferenceResult ActorReferenceResult::forReference(
   // FIXME: At the very least, we should consistently use
   // isActorInitOrDeInitContext here, but it only wants to think about actors.
   if (actorInstance && actorInstance->isSelf() &&
-      isStoredProperty(declRef.getDecl()) &&
+      isNonInheritedStorage(declRef.getDecl(), fromDC) &&
       declIsolation.isGlobalActor() &&
       (isa<ConstructorDecl>(fromDC) || isa<DestructorDecl>(fromDC)))
     return forSameConcurrencyDomain(declIsolation);

test/Concurrency/actor_isolation.swift

@@ -1497,3 +1497,31 @@ extension MyActor {
     }
   }
 }
+
+@MainActor
+class SuperWithNonisolatedInit {
+  static func isolatedToMainActor() {}
+
+  // expected-note@+1 2 {{mutation of this property is only permitted within the actor}}
+  var x: Int = 0 {
+    didSet {
+      SuperWithNonisolatedInit.isolatedToMainActor()
+    }
+  }
+
+  nonisolated init() {}
+}
+
+class OverridesNonsiolatedInit: SuperWithNonisolatedInit {
+  override nonisolated init() {
+    super.init()
+
+    // expected-error@+1 {{main actor-isolated property 'x' can not be mutated from a non-isolated context}}
+    super.x = 10
+  }
+
+  nonisolated func f() {
+    // expected-error@+1 {{main actor-isolated property 'x' can not be mutated from a non-isolated context}}
+    super.x = 10
+  }
+}