[Concurrency] Allow struct members to have isolation annotations.

include/swift/AST/DiagnosticsSema.def

@@ -5489,9 +5489,6 @@ ERROR(distributed_actor_remote_func_implemented_manually,none,
 ERROR(nonisolated_distributed_actor_storage,none,
       "'nonisolated' can not be applied to distributed actor stored properties",
       ())
-ERROR(nonisolated_storage_value_type,none,
-      "'nonisolated' is redundant on %0's stored properties",
-      (DescriptiveDeclKind))
 ERROR(distributed_actor_func_nonisolated, none,
       "cannot declare method %0 as both 'nonisolated' and 'distributed'",
       (DeclName))
@@ -5768,9 +5765,6 @@ ERROR(global_actor_on_actor_class,none,
       "actor %0 cannot have a global actor", (Identifier))
 ERROR(global_actor_on_local_variable,none,
       "local variable %0 cannot have a global actor", (DeclName))
-ERROR(global_actor_on_storage_of_value_type,none,
-      "stored property %0 within struct cannot have a global actor",
-      (DeclName))
 ERROR(unsafe_global_actor,none,
       "'(unsafe)' global actors are deprecated; "
       "use '@preconcurrency' instead",

lib/Sema/TypeCheckAttr.cpp

@@ -6909,17 +6909,6 @@ void AttributeChecker::visitNonisolatedAttr(NonisolatedAttr *attr) {
                                 diag::nonisolated_distributed_actor_storage);
           return;
         }
-
-        // 'nonisolated' is redundant for the stored properties of a struct.
-        if (isa<StructDecl>(nominal) &&
-            !var->isStatic() &&
-            var->isOrdinaryStoredProperty() &&
-            !isWrappedValueOfPropWrapper(var)) {
-          diagnoseAndRemoveAttr(attr, diag::nonisolated_storage_value_type,
-                                nominal->getDescriptiveKind())
-            .warnUntilSwiftVersion(6);
-          return;
-        }
       }
     }
 

lib/Sema/TypeCheckConcurrency.cpp

@@ -421,18 +421,6 @@ GlobalActorAttributeRequest::evaluate(
             .highlight(globalActorAttr->getRangeWithAt());
         return std::nullopt;
       }
-
-      // ... and not if it's the instance storage of a struct
-      if (isStoredInstancePropertyOfStruct(var)) {
-        var->diagnose(diag::global_actor_on_storage_of_value_type,
-                      var->getName())
-            .highlight(globalActorAttr->getRangeWithAt())
-            .warnUntilSwiftVersion(6);
-
-        // In Swift 6, once the diag above is an error, it is disallowed.
-        if (var->getASTContext().isSwiftVersionAtLeast(6))
-          return std::nullopt;
-      }
     }
   } else if (isa<ExtensionDecl>(decl)) {
     // Extensions are okay.

test/Concurrency/actor_isolation.swift

@@ -144,7 +144,7 @@ struct InferredFromContext {
   nonisolated var status: Bool = true // expected-error {{'nonisolated' cannot be applied to mutable stored properties}}{{3-15=}}{{3-15=}}{{14-14=(unsafe)}}
   // expected-note@-1{{convert 'status' to a 'let' constant or consider declaring it 'nonisolated(unsafe)' if manually managing concurrency safety}}
 
-  nonisolated let flag: Bool = false // expected-warning {{'nonisolated' is redundant on struct's stored properties; this is an error in the Swift 6 language mode}}{{3-15=}}
+  nonisolated let flag: Bool = false
 
   subscript(_ i: Int) -> Int { return i }
 
@@ -170,15 +170,13 @@ func checkIsolationValueType(_ formance: InferredFromConformance,
   _ = await NoGlobalActorValueType.polygon // expected-warning {{non-sendable type '[Point]' in implicitly asynchronous access to main actor-isolated static property 'polygon' cannot cross actor boundary}}
 }
 
-// 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 the Swift 6 language mode}}
 // 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 the Swift 6 language mode}}
+  @SomeGlobalActor var point: Point
   // 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 the Swift 6 language mode}}
+  @MainActor let counter: Int
 
   @MainActor static var polygon: [Point] = []
 }

test/Concurrency/actor_isolation_swift6.swift

@@ -36,7 +36,7 @@ struct InferredFromContext {
     get { [] }
   }
 
-  nonisolated let flag: Bool = false // expected-error {{'nonisolated' is redundant on struct's stored properties}}{{3-15=}}
+  nonisolated let flag: Bool = false
 
   subscript(_ i: Int) -> Int { return i }
 
@@ -49,15 +49,20 @@ func checkIsolationValueType(_ formance: InferredFromConformance,
   // these do not need an await, since it's a value type
   _ = ext.point
   _ = formance.counter
-  _ = anno.point
   _ = anno.counter
 
   // make sure it's just a warning if someone was awaiting on it previously
   _ = await ext.point // expected-warning {{no 'async' operations occur within 'await' expression}}
   _ = await formance.counter  // expected-warning {{no 'async' operations occur within 'await' expression}}
-  _ = await anno.point  // expected-warning {{no 'async' operations occur within 'await' expression}}
   _ = await anno.counter  // expected-warning {{no 'async' operations occur within 'await' expression}}
 
+  // We could extend the 'nonisolated within the module' rule to vars
+  // value types types if the property type is 'Sendable'.
+  _ = anno.point
+  // expected-error@-1 {{expression is 'async' but is not marked with 'await'}}
+  // expected-note@-2 {{property access is 'async'}}
+  _ = await anno.point
+
   // these do need await, regardless of reference or value type
   _ = await (formance as any MainCounter).counter
   // expected-error@-1 {{non-sendable type 'any MainCounter' passed in implicitly asynchronous call to main actor-isolated property 'counter' cannot cross actor boundary}}
@@ -68,11 +73,10 @@ func checkIsolationValueType(_ formance: InferredFromConformance,
   _ = await NoGlobalActorValueType.polygon
 }
 
-// check for instance members that do not need global-actor protection
 struct NoGlobalActorValueType {
-  @SomeGlobalActor var point: ImmutablePoint // expected-error {{stored property 'point' within struct cannot have a global actor}}
+  @SomeGlobalActor var point: ImmutablePoint
 
-  @MainActor let counter: Int // expected-error {{stored property 'counter' within struct cannot have a global actor}}
+  @MainActor let counter: Int
 
   @MainActor static var polygon: [ImmutablePoint] = []
 }

test/attr/global_actor.swift

@@ -67,7 +67,7 @@ struct OtherGlobalActor {
 }
 
 @GA1 struct X {
-  @GA1 var member: Int // expected-warning {{stored property 'member' within struct cannot have a global actor; this is an error in the Swift 6 language mode}}
+  @GA1 var member: Int
 }
 
 struct Y {