[Concurrency] Handle cases where a property initializer is subsumed by another

property for IsolatedDefaultValues.

For property wrappers and init accesors, skip property initializers that are
subsumed, e.g. by an init accessor or a backing property wrapper initializer,
and always consider the subsuming initializer to determine whether compiler
synthesized initializers should have `nonisolated` applied.

This change also lessens the source break of SE-0411 by still emitting
member initializers in implicit constructors when the initializer violates
actor isolation to preserve the behavior of existing code when concurrency
diagnostics are downgraded to warnings in Swift 5 mode.

Author: hborla

lib/SILGen/SILGenConstructor.cpp

@@ -1583,9 +1583,20 @@ void SILGenFunction::emitMemberInitializer(DeclContext *dc, VarDecl *selfDecl,
 
     case ActorIsolation::GlobalActor:
     case ActorIsolation::GlobalActorUnsafe:
-    case ActorIsolation::ActorInstance:
-      if (requiredIsolation != contextIsolation)
+    case ActorIsolation::ActorInstance: {
+      if (requiredIsolation != contextIsolation) {
+        // Implicit initializers diagnose actor isolation violations
+        // for property initializers in Sema. Still emit the invalid
+        // member initializer here to avoid duplicate diagnostics and
+        // to preserve warn-until-Swift-6 behavior.
+        auto *init =
+            dyn_cast_or_null<ConstructorDecl>(dc->getAsDecl());
+        if (init && init->isImplicit())
+          break;
+
         continue;
+      }
+    }
     }
 
     auto *varPattern = field->getPattern(i);

lib/Sema/CodeSynthesis.cpp

@@ -351,34 +351,59 @@ static ConstructorDecl *createImplicitConstructor(NominalTypeDecl *decl,
     // and actor initializers do not run on the actor, so initial values
     // cannot be actor-instance-isolated.
     bool shouldAddNonisolated = true;
-    llvm::Optional<ActorIsolation> existingIsolation = llvm::None;
+    ActorIsolation existingIsolation = getActorIsolation(decl);
     VarDecl *previousVar = nullptr;
 
-    // The memberwise init properties are also effectively what the
-    // default init uses, e.g. default initializers initialize via
-    // properties wrapped and init accessors.
-    for (auto var : decl->getMemberwiseInitProperties()) {
+    for (auto member : decl->getImplementationContext()->getAllMembers()) {
+      auto pbd = dyn_cast<PatternBindingDecl>(member);
+      if (!pbd || pbd->isStatic())
+        continue;
+
+      auto *var = pbd->getSingleVar();
+      if (!var) {
+        shouldAddNonisolated = false;
+        break;
+      }
+
+      auto i = pbd->getPatternEntryIndexForVarDecl(var);
+      if (pbd->isInitializerSubsumed(i))
+        continue;
+
+      ActorIsolation initIsolation;
+      if (var->hasInitAccessor()) {
+        // Init accessors share the actor isolation of the property;
+        // the accessor body can call anything in that isolation domain,
+        // and we don't attempt to infer when the isolation isn't
+        // necessary.
+        initIsolation = getActorIsolation(var);
+      } else {
+        initIsolation = var->getInitializerIsolation();
+      }
+
       auto type = var->getTypeInContext();
       auto isolation = getActorIsolation(var);
       if (isolation.isGlobalActor()) {
         if (!type->isSendableType() ||
-            var->getInitializerIsolation().isGlobalActor()) {
+            initIsolation.isGlobalActor()) {
           // If different isolated stored properties require different
           // global actors, it is impossible to initialize this type.
-          if (existingIsolation &&
-              *existingIsolation != isolation) {
+          if (existingIsolation != isolation) {
             ctx.Diags.diagnose(decl->getLoc(),
                 diag::conflicting_stored_property_isolation,
                 ICK == ImplicitConstructorKind::Memberwise,
-                decl->getDeclaredType(), *existingIsolation, isolation);
-            previousVar->diagnose(
-                diag::property_requires_actor,
-                previousVar->getDescriptiveKind(),
-                previousVar->getName(), *existingIsolation);
+                decl->getDeclaredType(), existingIsolation, isolation)
+              .warnUntilSwiftVersion(6);
+            if (previousVar) {
+              previousVar->diagnose(
+                  diag::property_requires_actor,
+                  previousVar->getDescriptiveKind(),
+                  previousVar->getName(), existingIsolation);
+            }
             var->diagnose(
                 diag::property_requires_actor,
                 var->getDescriptiveKind(),
                 var->getName(), isolation);
+            break;
           }
 
           existingIsolation = isolation;

test/Concurrency/actor_isolation.swift

@@ -168,9 +168,12 @@ func checkIsolationValueType(_ formance: InferredFromConformance,
 }
 
 // check for instance members that do not need global-actor protection
+
+// expected-warning@+2 {{memberwise initializer for 'NoGlobalActorValueType' cannot be both nonisolated and global actor 'SomeGlobalActor'-isolated; this is an error in Swift 6}}
 // expected-note@+1 2 {{consider making struct 'NoGlobalActorValueType' conform to the 'Sendable' protocol}}
 struct NoGlobalActorValueType {
   @SomeGlobalActor var point: Point // expected-warning {{stored property 'point' within struct cannot have a global actor; this is an error in Swift 6}}
+  // expected-note@-1 {{initializer for property 'point' is global actor 'SomeGlobalActor'-isolated}}
 
   @MainActor let counter: Int // expected-warning {{stored property 'counter' within struct cannot have a global actor; this is an error in Swift 6}}
 

test/Concurrency/global_actor_inference.swift

@@ -559,9 +559,13 @@ struct WrapperOnUnsafeActor<Wrapped> {
   }
 }
 
-// HasWrapperOnUnsafeActor gets an inferred @MainActor attribute.
+// HasWrapperOnUnsafeActor does not have an inferred global actor attribute,
+// because synced and $synced have different global actors.
 struct HasWrapperOnUnsafeActor {
-  @WrapperOnUnsafeActor var synced: Int = 0 // expected-complete-tns-warning {{global actor 'OtherGlobalActor'-isolated default value in a main actor-isolated context; this is an error in Swift 6}}
+// expected-complete-tns-warning@-1 {{memberwise initializer for 'HasWrapperOnUnsafeActor' cannot be both nonisolated and global actor 'OtherGlobalActor'-isolated; this is an error in Swift 6}}
+// expected-complete-tns-warning@-2 {{default initializer for 'HasWrapperOnUnsafeActor' cannot be both nonisolated and global actor 'OtherGlobalActor'-isolated; this is an error in Swift 6}}
+
+  @WrapperOnUnsafeActor var synced: Int = 0 // expected-complete-tns-note 2 {{initializer for property '_synced' is global actor 'OtherGlobalActor'-isolated}}
   // expected-note @-1 3{{property declared here}}
   // expected-complete-tns-note @-2 3{{property declared here}}
 
@@ -586,6 +590,10 @@ struct HasWrapperOnUnsafeActor {
   }
 }
 
+nonisolated func createHasWrapperOnUnsafeActor() {
+  _ = HasWrapperOnUnsafeActor()
+}
+
 // ----------------------------------------------------------------------
 // Nonisolated closures
 // ----------------------------------------------------------------------
@@ -670,7 +678,9 @@ func replacesDynamicOnMainActor() {
 // Global-actor isolation of stored property initializer expressions
 // ----------------------------------------------------------------------
 
+// expected-complete-tns-warning@+1 {{default initializer for 'Cutter' cannot be both nonisolated and main actor-isolated; this is an error in Swift 6}}
 class Cutter {
+  // expected-complete-tns-note@+1 {{initializer for property 'x' is main actor-isolated}}
   @MainActor var x = useFooInADefer()
   @MainActor var y = { () -> Bool in
       var z = statefulThingy

test/Concurrency/isolated_default_arguments.swift

@@ -1,7 +1,5 @@
 // RUN: %empty-directory(%t)
 
-// RUN: %target-swift-frontend -emit-module -emit-module-path %t/OtherActors.swiftmodule -module-name OtherActors %S/Inputs/OtherActors.swift -disable-availability-checking
-
 // RUN: %target-swift-frontend -I %t  -disable-availability-checking -strict-concurrency=complete -enable-upcoming-feature IsolatedDefaultValues -parse-as-library -emit-sil -o /dev/null -verify %s
 // RUN: %target-swift-frontend -I %t  -disable-availability-checking -strict-concurrency=complete -parse-as-library -emit-sil -o /dev/null -verify -enable-upcoming-feature IsolatedDefaultValues -enable-experimental-feature RegionBasedIsolation %s
 
@@ -196,21 +194,19 @@ extension A {
   }
 }
 
-// expected-error@+1 {{default initializer for 'C1' cannot be both main actor-isolated and global actor 'SomeGlobalActor'-isolated}}
+// expected-warning@+1 {{default initializer for 'C1' cannot be both nonisolated and main actor-isolated; this is an error in Swift 6}}
 class C1 {
   // expected-note@+1 {{initializer for property 'x' is main actor-isolated}}
   @MainActor var x = requiresMainActor()
-  // expected-note@+1 {{initializer for property 'y' is global actor 'SomeGlobalActor'-isolated}}
   @SomeGlobalActor var y = requiresSomeGlobalActor()
 }
 
 class NonSendable {}
 
-// expected-error@+1 {{default initializer for 'C2' cannot be both main actor-isolated and global actor 'SomeGlobalActor'-isolated}}
+// expected-warning@+1 {{default initializer for 'C2' cannot be both nonisolated and main actor-isolated; this is an error in Swift 6}}
 class C2 {
   // expected-note@+1 {{initializer for property 'x' is main actor-isolated}}
   @MainActor var x = NonSendable()
-  // expected-note@+1 {{initializer for property 'y' is global actor 'SomeGlobalActor'-isolated}}
   @SomeGlobalActor var y = NonSendable()
 }
 
@@ -229,3 +225,42 @@ func callDefaultInit() async {
   _ = NonIsolatedInit()
   _ = NonIsolatedInit(x: 10)
 }
+
+@propertyWrapper 
+@preconcurrency @MainActor
+struct RequiresMain<Value>  {
+  var wrappedValue: Value
+
+  init(wrappedValue: Value) {
+    self.wrappedValue = wrappedValue
+  }
+}
+
+// This is okay; UseRequiresMain has an inferred 'MainActor'
+// attribute.
+struct UseRequiresMain {
+  @RequiresMain private var x = 10
+}
+
+nonisolated func test() async {
+  // expected-warning@+2 {{expression is 'async' but is not marked with 'await'; this is an error in Swift 6}}
+  // expected-note@+1 {{calls to initializer 'init()' from outside of its actor context are implicitly asynchronous}}
+  _ = UseRequiresMain()
+}
+
+// expected-warning@+2 {{memberwise initializer for 'InitAccessors' cannot be both nonisolated and main actor-isolated; this is an error in Swift 6}}
+// expected-warning@+1 {{default initializer for 'InitAccessors' cannot be both nonisolated and main actor-isolated; this is an error in Swift 6}}
+struct InitAccessors {
+  private var _a: Int
+
+  // expected-note@+1 2 {{initializer for property 'a' is main actor-isolated}}
+  @MainActor var a: Int = 5 {
+    @storageRestrictions(initializes: _a)
+    init {
+      _a = requiresMainActor()
+    }
+    get {
+      _a
+    }
+  }
+}