[Concurrency] Allow isolation on subclasses of non-Sendable, non-isolated

superclasses.

(cherry picked from commit 87f49a5)

Author: hborla

lib/Sema/TypeCheckConcurrency.cpp

@@ -4805,9 +4805,14 @@ static bool checkClassGlobalActorIsolation(
   switch (superIsolation) {
   case ActorIsolation::Unspecified:
   case ActorIsolation::Nonisolated:
-  case ActorIsolation::NonisolatedUnsafe:
+  case ActorIsolation::NonisolatedUnsafe: {
+    auto &ctx = classDecl->getASTContext();
+    if (ctx.LangOpts.hasFeature(Feature::GlobalActorIsolatedTypesUsability))
+      return false;
+
     downgradeToWarning = true;
     break;
+  }
 
   case ActorIsolation::Erased:
     llvm_unreachable("class cannot have erased isolation");
@@ -6046,6 +6051,13 @@ ProtocolConformance *swift::deriveImplicitSendableConformance(
               inheritedConformance.getConcrete());
         }
       }
+
+      // Classes that add global actor isolation to non-Sendable
+      // superclasses cannot be 'Sendable'.
+      if (ctx.LangOpts.hasFeature(Feature::GlobalActorIsolatedTypesUsability) &&
+          nominal->getGlobalActorAttr()) {
+        return nullptr;
+      }
     }
   }
 

test/Concurrency/actor_isolation.swift

@@ -1282,8 +1282,14 @@ actor Counter {
 class C2 { }
 
 @SomeGlobalActor
-class C3: C2 { }
-// expected-warning@-1 {{global actor 'SomeGlobalActor'-isolated class 'C3' has different actor isolation from nonisolated superclass 'C2'; this is an error in the Swift 6 language mode}}
+class C3: C2 { // expected-note {{class 'C3' does not conform to the 'Sendable' protocol}}
+  func requireSendableSelf() {
+    Task.detached {
+      _ = self
+      // expected-warning@-1 {{capture of 'self' with non-sendable type 'C3' in a `@Sendable` closure; this is an error in the Swift 6 language mode}}
+    }
+  }
+}
 
 @GenericGlobalActor<U>
 class GenericSuper<U> { }
@@ -1463,7 +1469,6 @@ class None {
 // try to add inferred isolation while overriding
 @MainActor
 class MA_None1: None {
-// expected-warning@-1 {{main actor-isolated class 'MA_None1' has different actor isolation from nonisolated superclass 'None'; this is an error in the Swift 6 language mode}}
 
   // FIXME: bad note, since the problem is a mismatch in overridden vs inferred isolation; this wont help.
   // expected-note@+1 {{add '@MainActor' to make instance method 'method()' part of global actor 'MainActor'}}
@@ -1494,7 +1499,6 @@ class None_MADirect: MADirect {
 
 @SomeGlobalActor
 class SGA_MADirect: MADirect {
-// expected-warning@-1 {{global actor 'SomeGlobalActor'-isolated class 'SGA_MADirect' has different actor isolation from nonisolated superclass 'MADirect'; this is an error in the Swift 6 language mode}}
 
   // inferred-SomeGlobalActor vs overridden-MainActor = mainactor
   override func method1() { beets_ma() }

test/Concurrency/global_actor_inference.swift

@@ -248,8 +248,6 @@ class SuperclassWithGlobalActors {
 
 @GenericGlobalActor<String>
 class SubclassWithGlobalActors : SuperclassWithGlobalActors {
-// expected-warning@-1 {{global actor 'GenericGlobalActor<String>'-isolated class 'SubclassWithGlobalActors' has different actor isolation from nonisolated superclass 'SuperclassWithGlobalActors'; this is an error in the Swift 6 language mode}}
-
   override func f() { } // okay: inferred to @GenericGlobalActor<Int>
 
   @GenericGlobalActor<String> override func g() { } // expected-error{{global actor 'GenericGlobalActor<String>'-isolated instance method 'g()' has different actor isolation from global actor 'GenericGlobalActor<Int>'-isolated overridden declaration}}