[SE-0306] Disable actor inheritance.

include/swift/AST/DiagnosticsSema.def

@@ -4351,8 +4351,8 @@ NOTE(objc_ambiguous_async_convention_candidate,none,
 ERROR(async_objc_dynamic_self,none,
       "asynchronous method returning 'Self' cannot be '@objc'", ())
 
-ERROR(actor_with_nonactor_superclass,none,
-      "actor cannot inherit from non-actor class %0", (DeclName))
+ERROR(actor_inheritance,none,
+      "actor types do not support inheritance", ())
 
 ERROR(actor_isolated_non_self_reference,none,
         "actor-isolated %0 %1 can only be %select{referenced|mutated|used 'inout'}3 "

lib/Sema/TypeCheckConcurrency.cpp

@@ -270,32 +270,8 @@ bool IsActorRequest::evaluate(
   if (!classDecl)
     return false;
 
-  bool isExplicitActor = classDecl->isExplicitActor() ||
-    classDecl->getAttrs().getAttribute<ActorAttr>();
-
-  // If there is a superclass, we can infer actor-ness from it.
-  if (auto superclassDecl = classDecl->getSuperclassDecl()) {
-    // The superclass is an actor, so we are, too.
-    if (superclassDecl->isActor())
-      return true;
-
-    // The superclass is 'NSObject', which is known to have no state and no
-    // superclass.
-    if (superclassDecl->isNSObject() && isExplicitActor)
-      return true;
-
-    // This class cannot be an actor; complain if the 'actor' modifier was
-    // provided.
-    if (isExplicitActor) {
-      classDecl->diagnose(diag::actor_with_nonactor_superclass,
-                          superclassDecl->getName())
-        .highlight(classDecl->getStartLoc());
-    }
-
-    return false;
-  }
-
-  return isExplicitActor;
+  return classDecl->isExplicitActor() ||
+      classDecl->getAttrs().getAttribute<ActorAttr>();
 }
 
 bool IsDefaultActorRequest::evaluate(
@@ -305,21 +281,6 @@ bool IsDefaultActorRequest::evaluate(
   if (!classDecl->isActor())
     return false;
 
-  // If there is a superclass, and it's an actor, we defer
-  // the decision to it.
-  if (auto superclassDecl = classDecl->getSuperclassDecl()) {
-    // If the superclass is an actor, we inherit its default-actor-ness.
-    if (superclassDecl->isActor())
-      return superclassDecl->isDefaultActor();
-
-    // If the superclass is not an actor, it can only be
-    // a default actor if it's NSObject.  (For now, other classes simply
-    // can't be actors at all.)  We don't need to diagnose this; we
-    // should've done that already in isActor().
-    if (!superclassDecl->isNSObject())
-      return false;
-  }
-
   // If the class is resilient from the perspective of the module
   // module, it's not a default actor.
   if (classDecl->isForeign() || classDecl->isResilient(M, expansion))

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -2314,6 +2314,14 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     // Check for circular inheritance.
     (void)CD->getSuperclassDecl();
 
+    if (auto superclass = CD->getSuperclassDecl()) {
+      // Actors cannot have superclasses, nor can they be superclasses.
+      if (CD->isActor() && !superclass->isNSObject())
+        CD->diagnose(diag::actor_inheritance);
+      else if (superclass->isActor())
+        CD->diagnose(diag::actor_inheritance);
+    }
+
     // Force lowering of stored properties.
     (void) CD->getStoredProperties();
 

test/Concurrency/actor_isolation.swift

@@ -48,7 +48,7 @@ class Point {
 }
 
 @available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *)
-actor MyActor: MySuperActor {
+actor MyActor: MySuperActor { // expected-error{{actor types do not support inheritance}}
   nonisolated let immutable: Int = 17
   // expected-note@+2 2{{property declared here}}
   // expected-note@+1 6{{mutation of this property is only permitted within the actor}}

test/Concurrency/async_initializer.swift

@@ -91,8 +91,7 @@ actor A {
   }
 }
 
-// NOTE: actor inheritance is probably being removed soon, so just remove this def of B
-actor B: A {
+actor B: A { // expected-error{{actor types do not support inheritance}}
   init(x : String) async {} // expected-error {{missing call to superclass's initializer; 'super.init' is 'async' and requires an explicit call}}
 }
 

test/Concurrency/global_actor_inference.swift

@@ -173,7 +173,7 @@ actor GenericSuper<T> {
   @GenericGlobalActor<T> func method5() { }
 }
 
-actor GenericSub<T> : GenericSuper<[T]> {
+actor GenericSub<T> : GenericSuper<[T]> { // expected-error{{actor types do not support inheritance}}
   override func method() { }  // expected-note {{calls to instance method 'method()' from outside of its actor context are implicitly asynchronous}}
 
   @GenericGlobalActor<T> override func method2() { } // expected-error{{global actor 'GenericGlobalActor<T>'-isolated instance method 'method2()' has different actor isolation from global actor 'GenericGlobalActor<[T]>'-isolated overridden declaration}}

test/IRGen/actor_class_forbid_objc_assoc_objects.swift

@@ -15,10 +15,6 @@ final actor Actor {
 actor Actor2 {
 }
 
-// CHECK: @_METACLASS_DATA__TtC37actor_class_forbid_objc_assoc_objects6Actor3 = internal constant { {{.*}} } { i32 [[METAFLAGS]],
-// CHECK: @_DATA__TtC37actor_class_forbid_objc_assoc_objects6Actor3 = internal constant { {{.*}} } { i32 [[OBJECTFLAGS]],
-class Actor3 : Actor2 {}
-
 actor GenericActor<T> {
     var state: T
     init(state: T) { self.state = state }

test/IRGen/async/Inputs/resilient_actor.swift

@@ -2,11 +2,6 @@ open actor ResilientBaseActor {
   public init() {}
 }
 
-@_fixed_layout
-open actor FixedSubclassOfResilientBaseActor : ResilientBaseActor {
-  public override init() {}
-}
-
 @_fixed_layout
 open actor FixedBaseActor {
   public init() {}

test/IRGen/async/default_actor.swift

@@ -8,40 +8,10 @@
 //   0x81010050: the same, but using a singleton metadata initialization
 // CHECK-SAME: i32 {{-2130706352|-2130640816}},
 
-// CHECK: @"$s13default_actor1BCMn" = hidden constant
-//   0x62010050: 0x02000000 IndirectTypeDescriptor + 0x01000000 IsDefaultActor
-// CHECK-SAME: i32 1644232784,
-
-// CHECK: @"$s13default_actor1CCMn" = hidden constant
-//   0x62010050: 0x02000000 IndirectTypeDescriptor + 0x01000000 IsDefaultActor
-// CHECK-SAME: i32 1644232784,
-
-// CHECK: @"$s13default_actor1DCMn" = hidden constant
-//   0x63010050: 0x02000000 IndirectTypeDescriptor + 0x01000000 IsDefaultActor
-// CHECK-SAME: i32 1661010000,
-
 import resilient_actor
 
 // CHECK-LABEL: define hidden swiftcc void @"$s13default_actor1ACfD"(%T13default_actor1AC* swiftself %0)
 // CHECK-NOT: ret void
 // CHECK:     call swiftcc void @swift_defaultActor_deallocate(
 // CHECK:     ret void
 actor A {}
-
-// CHECK-LABEL: define hidden swiftcc void @"$s13default_actor1BCfD"(%T13default_actor1BC* swiftself %0)
-// CHECK-NOT: ret void
-// CHECK:     call swiftcc void @swift_defaultActor_deallocateResilient(
-// CHECK:     ret void
-actor B : ResilientBaseActor {}
-
-// CHECK-LABEL: define hidden swiftcc void @"$s13default_actor1CCfD"(%T13default_actor1CC* swiftself %0)
-// CHECK-NOT: ret void
-// CHECK:     call swiftcc void @swift_defaultActor_deallocateResilient(
-// CHECK:     ret void
-actor C : FixedSubclassOfResilientBaseActor {}
-
-// CHECK-LABEL: define hidden swiftcc void @"$s13default_actor1DCfD"(%T13default_actor1DC* swiftself %0)
-// CHECK-NOT: ret void
-// CHECK:     call swiftcc void @swift_defaultActor_deallocate(
-// CHECK:     ret void
-actor D : FixedBaseActor {}

test/Interpreter/actor_class_forbid_objc_assoc_objects.swift

@@ -44,48 +44,6 @@ if #available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *) {
   }
 }
 
-@available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *)
-class Actor3 : Actor2 {}
-
-if #available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *) {
-  Tests.test("non-final subclass crash when set assoc object")
-  .crashOutputMatches("objc_setAssociatedObject called on instance")
-  .code {
-    expectCrashLater()
-    let x = Actor3()
-    objc_setAssociatedObject(x, "myKey", "myValue", .OBJC_ASSOCIATION_RETAIN)
-  }
-}
-
-@available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *)
-final class Actor3Final : Actor2 {}
-
-if #available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *) {
-  Tests.test("final subclass crash when set assoc object")
-  .crashOutputMatches("objc_setAssociatedObject called on instance")
-  .code {
-    expectCrashLater()
-    let x = Actor3Final()
-    objc_setAssociatedObject(x, "myKey", "myValue", .OBJC_ASSOCIATION_RETAIN)
-  }
-}
-
-@available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *)
-class Actor4<T> : Actor2 {
-  var state: T
-  init(state: T) { self.state = state }
-}
-
-if #available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *) {
-  Tests.test("generic subclass crash when set assoc object")
-  .crashOutputMatches("objc_setAssociatedObject called on instance")
-  .code {
-    expectCrashLater()
-    let x = Actor4(state: 5)
-    objc_setAssociatedObject(x, "myKey", "myValue", .OBJC_ASSOCIATION_RETAIN)
-  }
-}
-
 @available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *)
 actor Actor5<T> {
   var state: T
@@ -110,50 +68,6 @@ if #available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *) {
   }
 }
 
-@available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *)
-class Actor6<T> : Actor5<T> {
-  override init(state: T) { super.init(state: state) }
-}
-
-if #available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *) {
-  Tests.test("sub-generic class base generic class crash when set assoc object")
-  .crashOutputMatches("objc_setAssociatedObject called on instance")
-  .code {
-    expectCrashLater()
-    let x = Actor6(state: 5)
-    objc_setAssociatedObject(x, "myKey", "myValue", .OBJC_ASSOCIATION_RETAIN)
-  }
-}
-
-@available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *)
-final class Actor6Final<T> : Actor5<T> {
-  override init(state: T) { super.init(state: state) }
-}
-
-if #available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *) {
-  Tests.test("final sub-generic class base generic class crash when set assoc object")
-  .crashOutputMatches("objc_setAssociatedObject called on instance")
-  .code {
-    expectCrashLater()
-    let x = Actor6Final(state: 5)
-    objc_setAssociatedObject(x, "myKey", "myValue", .OBJC_ASSOCIATION_RETAIN)
-  }
-
-  Tests.test("final sub-generic class base generic class crash when set assoc object2")
-  .code {
-    let x = Actor6Final(state: 5)
-    print(type(of: x))
-  }
-
-  Tests.test("final sub-generic class metatype, base generic class crash when set assoc object")
-  .crashOutputMatches("objc_setAssociatedObject called on instance")
-  .code {
-    expectCrashLater()
-    let x = Actor6Final<Int>.self
-    objc_setAssociatedObject(x, "myKey", "myValue", .OBJC_ASSOCIATION_RETAIN)
-  }
-}
-
 @available(macOS 10.4.4, iOS 12.2, watchOS 5.2, tvOS 12.2, *)
 actor ActorNSObjectSubKlass : NSObject {}
 

test/Interpreter/actor_subclass_metatypes.swift

@@ -26,23 +26,3 @@ Tests.test("base generic class")
   let x = Actor5(state: 5)
   print(type(of: x))
 }
-
-class Actor6<T> : Actor5<T> {
-  override init(state: T) { super.init(state: state) }
-}
-
-Tests.test("non-final sub-generic class parent generic class crash")
-  .code {
-  let x = Actor6(state: 5)
-  print(type(of: x))
-}
-
-final class Actor6Final<T> : Actor5<T> {
-  override init(state: T) { super.init(state: state) }
-}
-
-Tests.test("final sub-generic class parent generic class crash")
-  .code {
-  let x = Actor6Final(state: 5)
-  print(type(of: x))
-}

test/ModuleInterface/actor_isolation.swift

@@ -38,9 +38,3 @@ public class C2 { }
 
 // CHECK: @{{(Test.)?}}SomeGlobalActor public class C2
 public class C3: C2 { }
-
-// CHECK: public actor SomeSubActor
-// CHECK-NEXT: @actorIndependent public func maine()
-public actor SomeSubActor: SomeActor {
-  override public func maine() { }
-}

test/decl/class/actor/basic.swift

@@ -4,16 +4,17 @@
 
 actor MyActor { }
 
-class MyActorSubclass1: MyActor { }
+class MyActorSubclass1: MyActor { } // expected-error{{actor types do not support inheritance}}
+// expected-error@-1{{non-final class 'MyActorSubclass1' cannot conform to `Sendable`; use `UnsafeSendable`}}
 
-actor MyActorSubclass2: MyActor { }
+actor MyActorSubclass2: MyActor { } // expected-error{{actor types do not support inheritance}}
 
 // expected-warning@+1{{'actor class' has been renamed to 'actor'}}{{7-13=}}
 actor class MyActorClass { }
 
 class NonActor { }
 
-actor NonActorSubclass : NonActor { } // expected-error{{actor cannot inherit from non-actor class 'NonActor'}}
+actor NonActorSubclass : NonActor { } // expected-error{{actor types do not support inheritance}}
 
 // expected-warning@+1{{'actor class' has been renamed to 'actor'}}{{14-20=}}
 public actor class BobHope {}

test/decl/protocol/special/Actor.swift

@@ -19,16 +19,17 @@ actor A3<T>: Actor {
 }
 
 @available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *)
-actor A4: A1 {
+actor A4: A1 { // expected-error{{actor types do not support inheritance}}
 }
 
 @available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *)
-actor A5: A2 {
+actor A5: A2 { // expected-error{{actor types do not support inheritance}}
 }
 
 @available(macOS 9999, iOS 9999, watchOS 9999, tvOS 9999, *)
 actor A6: A1, Actor { // expected-error{{redundant conformance of 'A6' to protocol 'Actor'}}
   // expected-note@-1{{'A6' inherits conformance to protocol 'Actor' from superclass here}}
+  // expected-error@-2{{actor types do not support inheritance}}
 }
 
 // Explicitly satisfying the requirement.