Disable actor inference from property wrapper usage

include/swift/Basic/Features.def

@@ -114,6 +114,7 @@ UPCOMING_FEATURE(ForwardTrailingClosures, 286, 6)
 UPCOMING_FEATURE(BareSlashRegexLiterals, 354, 6)
 UPCOMING_FEATURE(ExistentialAny, 335, 6)
 UPCOMING_FEATURE(ImportObjcForwardDeclarations, 384, 6)
+UPCOMING_FEATURE(DisableActorInferenceFromPropertyWrapperUsage, 401, 6)
 
 EXPERIMENTAL_FEATURE(StaticAssert, false)
 EXPERIMENTAL_FEATURE(NamedOpaqueTypes, false)

lib/AST/ASTPrinter.cpp

@@ -3346,6 +3346,11 @@ static bool usesFeatureBuiltinMacros(Decl *decl) {
   return false;
 }
 
+
+static bool usesFeatureDisableActorInferenceFromPropertyWrapperUsage(Decl *decl) {
+  return false;
+}
+
 static bool usesFeatureImportSymbolicCXXDecls(Decl *decl) { return false; }
 
 static bool usesFeatureGenerateBindingsForThrowingFunctionsInCXX(Decl *decl) {

lib/Sema/TypeCheckConcurrency.cpp

@@ -3653,6 +3653,13 @@ getIsolationFromWrappers(NominalTypeDecl *nominal) {
   if (!nominal->getParentSourceFile())
     return llvm::None;
 
+  ASTContext &ctx = nominal->getASTContext();
+  if (ctx.LangOpts.hasFeature(Feature::DisableActorInferenceFromPropertyWrapperUsage)) {
+    // In Swift 6, we no longer infer isolation of a nominal type
+    // based on the property wrappers used in its stored properties
+    return llvm::None;
+  }
+
   llvm::Optional<ActorIsolation> foundIsolation;
   for (auto member : nominal->getMembers()) {
     auto var = dyn_cast<VarDecl>(member);
@@ -4266,8 +4273,8 @@ ActorIsolation ActorIsolationRequest::evaluate(
         if (auto inferred = inferredIsolation(*conformanceIsolation))
           return inferred;
 
-      // If the declaration is a nominal type and any property wrappers on
-      // its stored properties require isolation, use that.
+      // Before Swift 6: If the declaration is a nominal type and any property
+      // wrappers on its stored properties require isolation, use that.
       if (auto wrapperIsolation = getIsolationFromWrappers(nominal)) {
         if (auto inferred = inferredIsolation(*wrapperIsolation))
           return inferred;

test/Concurrency/global_actor_inference_swift6.swift

@@ -78,7 +78,7 @@ struct HasMainActorWrappedProp {
 
   var plainStorage: Int
 
-  var computedProp: Int { 0 } // expected-note {{property declared here}}
+  var computedProp: Int { 0 }
 
   nonisolated func testErrors() {
     _ = thing // expected-error {{main actor-isolated property 'thing' can not be referenced from a non-isolated context}}
@@ -89,7 +89,7 @@ struct HasMainActorWrappedProp {
 
     _ = plainStorage
 
-    _ = computedProp // expected-error {{main actor-isolated property 'computedProp' can not be referenced from a non-isolated context}}
+    _ = computedProp
   }
 }