[Concurrency] Un-gate implicit nonisolated access to struct vars and isolated

subclassing.

These features are additive, and they don't need to be gated behind the
`GlobalActorIsolatedTypesUsability` upcoming feature. The other inference
changes, including `@Sendable` inference for global-actor-isolated function
types, and global-actor inference on protocol refinements, remain gated
behind the upcoming flag.

Author: hborla

lib/Sema/TypeCheckConcurrency.cpp

@@ -512,16 +512,14 @@ static bool varIsSafeAcrossActors(const ModuleDecl *fromModule,
 
   if (!var->isLet()) {
     ASTContext &ctx = var->getASTContext();
-    if (ctx.LangOpts.hasFeature(Feature::GlobalActorIsolatedTypesUsability)) {
-      // A mutable storage of a value type accessed from within the module is
-      // okay.
-      if (dyn_cast_or_null<StructDecl>(var->getDeclContext()->getAsDecl()) &&
-          !var->isStatic() && 
-          var->hasStorage() &&
-          var->getTypeInContext()->isSendableType() &&
-          accessWithinModule) {
-        return true;
-      }
+    // A mutable storage of a value type accessed from within the module is
+    // okay.
+    if (dyn_cast_or_null<StructDecl>(var->getDeclContext()->getAsDecl()) &&
+        !var->isStatic() &&
+        var->hasStorage() &&
+        var->getTypeInContext()->isSendableType() &&
+        accessWithinModule) {
+      return true;
     }
     // Otherwise, must be immutable.
     return false;
@@ -4808,12 +4806,7 @@ static bool checkClassGlobalActorIsolation(
   case ActorIsolation::Unspecified:
   case ActorIsolation::Nonisolated:
   case ActorIsolation::NonisolatedUnsafe: {
-    auto &ctx = classDecl->getASTContext();
-    if (ctx.LangOpts.hasFeature(Feature::GlobalActorIsolatedTypesUsability))
-      return false;
-
-    downgradeToWarning = true;
-    break;
+    return false;
   }
 
   case ActorIsolation::Erased:
@@ -6054,8 +6047,8 @@ ProtocolConformance *swift::deriveImplicitSendableConformance(
 
       // Classes that add global actor isolation to non-Sendable
       // superclasses cannot be 'Sendable'.
-      if (ctx.LangOpts.hasFeature(Feature::GlobalActorIsolatedTypesUsability) &&
-          nominal->getGlobalActorAttr()) {
+      auto superclassDecl = classDecl->getSuperclassDecl();
+      if (nominal->getGlobalActorAttr() && !superclassDecl->isNSObject()) {
         return nullptr;
       }
     }

test/ClangImporter/objc_async.swift

@@ -298,7 +298,7 @@ class BarFrame: PictureFrame {
 @available(SwiftStdlib 5.5, *)
 @SomeGlobalActor
 class BazFrame: NotIsolatedPictureFrame {
-// expected-warning@-1 {{global actor 'SomeGlobalActor'-isolated class 'BazFrame' has different actor isolation from nonisolated superclass 'NotIsolatedPictureFrame'; this is an error in the Swift 6 language mode}}
+// expected-note@-1 2 {{class 'BazFrame' does not conform to the 'Sendable' protocol}}
   init() {
     super.init(size: 0)
   }
@@ -322,10 +322,12 @@ func check() async {
   _ = await BarFrame()
   _ = await FooFrame()
   _ = await BazFrame()
+  // expected-warning@-1 {{non-sendable type 'BazFrame' returned by call to global actor 'SomeGlobalActor'-isolated function cannot cross actor boundary; this is an error in the Swift 6 language mode}}
 
   _ = await BarFrame(size: 0)
   _ = await FooFrame(size: 0)
   _ = await BazFrame(size: 0)
+  // expected-warning@-1 {{non-sendable type 'BazFrame' returned by call to global actor 'SomeGlobalActor'-isolated function cannot cross actor boundary; this is an error in the Swift 6 language mode}}
 }
 
 @available(SwiftStdlib 5.5, *)

test/Concurrency/sendable_checking.swift

@@ -239,7 +239,7 @@ func testConversionsAndSendable(a: MyActor, s: any Sendable, f: @Sendable () ->
 
 @available(SwiftStdlib 5.1, *)
 final class NonSendable {
-  // expected-note @-1 3 {{class 'NonSendable' does not conform to the 'Sendable' protocol}}
+  // expected-note @-1 4 {{class 'NonSendable' does not conform to the 'Sendable' protocol}}
   // TransferNonSendable emits 3 fewer errors here.
   // expected-targeted-and-complete-note @-3 5 {{class 'NonSendable' does not conform to the 'Sendable' protocol}}
   // expected-complete-and-tns-note @-4 {{class 'NonSendable' does not conform to the 'Sendable' protocol}}
@@ -397,12 +397,13 @@ struct DowngradeForPreconcurrency {
     }
   }
 
-  var x: Int
-  func createStream() -> AsyncStream<Int> {
-    AsyncStream<Int> {
+  var x: NonSendable
+  func createStream() -> AsyncStream<NonSendable> {
+    AsyncStream<NonSendable> {
       self.x
       // expected-warning@-1 {{expression is 'async' but is not marked with 'await'; this is an error in the Swift 6 language mode}}
       // expected-note@-2 {{property access is 'async'}}
+      // expected-warning@-3 {{non-sendable type 'NonSendable' in implicitly asynchronous access to main actor-isolated property 'x' cannot cross actor boundary; this is an error in the Swift 6 language mode}}
     }
   }
 }

test/SILGen/hop_to_executor_async_prop.swift

@@ -588,10 +588,8 @@ struct Container {
     // CHECK: [[SOME_BB]]:
     // CHECK:       [[DATA_ADDR:%[0-9]+]] = unchecked_take_enum_data_addr [[ACCESS]] : $*Optional<Container>, #Optional.some!enumelt
     // CHECK:       [[ELEM_ADDR:%[0-9]+]] = struct_element_addr [[DATA_ADDR]] : $*Container, #Container.iso
-    // CHECK:       hop_to_executor {{%[0-9]+}} : $Cat
     // CHECK:       {{%[0-9]+}} = load [trivial] [[ELEM_ADDR]] : $*Float
     // CHECK:       hop_to_executor [[GENERIC_EXEC]] :
-    // CHECK:       hop_to_executor [[GENERIC_EXEC]] :
     // CHECK: } // end sil function '$s4test9ContainerV10getOrCrashSfyYaFZ'
     static func getOrCrash() async -> Float {
         return await this!.iso
@@ -628,7 +626,7 @@ struct Container {
 
 @propertyWrapper
 struct StateObject<ObjectType> {
-    @MainActor(unsafe)
+    @preconcurrency @MainActor
     var wrappedValue: ObjectType {
         fatalError()
     }