[Concurrency] Start diagnosing use of global actor isolated properties in key paths

If key path is formed in a concurrency domain different from the
one where the member is, diagnose that as a warning until Swift 6.

Author: xedin

lib/Sema/TypeCheckConcurrency.cpp

@@ -3343,8 +3343,8 @@ namespace {
       for (const auto &component : keyPath->getComponents()) {
         // The decl referred to by the path component cannot be within an actor.
         if (component.hasDeclRef()) {
-          auto concDecl = component.getDeclRef();
-          auto decl = concDecl.getDecl();
+          auto declRef = component.getDeclRef();
+          auto decl = declRef.getDecl();
           auto isolation = getActorIsolationForReference(
               decl, getDeclContext());
           switch (isolation) {
@@ -3354,13 +3354,16 @@ namespace {
             break;
 
           case ActorIsolation::GlobalActor:
-          case ActorIsolation::GlobalActorUnsafe:
-            // Disable global actor checking for now.
-            if (isolation.isGlobalActor() &&
-                !ctx.LangOpts.isSwiftVersionAtLeast(6))
+          case ActorIsolation::GlobalActorUnsafe: {
+            auto result = ActorReferenceResult::forReference(
+                declRef, component.getLoc(), getDeclContext(),
+                kindOfUsage(decl, keyPath));
+
+            if (result == ActorReferenceResult::SameConcurrencyDomain)
               break;
 
             LLVM_FALLTHROUGH;
+          }
 
           case ActorIsolation::ActorInstance:
             // If this entity is always accessible across actors, just check
@@ -3376,11 +3379,17 @@ namespace {
               break;
             }
 
-            ctx.Diags.diagnose(component.getLoc(),
-                               diag::actor_isolated_keypath_component,
-                               isolation.isDistributedActor(),
-                               decl);
-            diagnosed = true;
+            {
+              auto diagnostic = ctx.Diags.diagnose(
+                  component.getLoc(), diag::actor_isolated_keypath_component,
+                  isolation.isDistributedActor(), decl);
+
+              if (isolation == ActorIsolation::ActorInstance)
+                diagnosed = true;
+              else
+                diagnostic.warnUntilSwiftVersion(6);
+            }
+
             break;
           }
         }

test/Concurrency/actor_keypath_isolation.swift

@@ -58,7 +58,7 @@ func tryKeyPathsMisc(d : Door) {
 
 func tryKeyPathsFromAsync() async {
     _ = \Door.unsafeGlobActor_immutable
-    _ = \Door.unsafeGlobActor_mutable // okay for now
+    _ = \Door.unsafeGlobActor_mutable // expected-warning {{cannot form key path to actor-isolated property 'unsafeGlobActor_mutable'; this is an error in Swift 6}}
 }
 
 func tryNonSendable() {
@@ -69,7 +69,7 @@ func tryNonSendable() {
 
 func tryKeypaths() {
     _ = \Door.unsafeGlobActor_immutable
-    _ = \Door.unsafeGlobActor_mutable // okay for now
+    _ = \Door.unsafeGlobActor_mutable // expected-warning {{cannot form key path to actor-isolated property 'unsafeGlobActor_mutable'; this is an error in Swift 6}}
 
     _ = \Door.immutable
     _ = \Door.globActor_immutable
@@ -84,7 +84,7 @@ func tryKeypaths() {
     let _ : PartialKeyPath<Door> = \.mutable // expected-error{{cannot form key path to actor-isolated property 'mutable'}}
     let _ : AnyKeyPath = \Door.mutable  // expected-error{{cannot form key path to actor-isolated property 'mutable'}}
 
-    _ = \Door.globActor_mutable // okay for now
+    _ = \Door.globActor_mutable // expected-warning {{cannot form key path to actor-isolated property 'globActor_mutable'; this is an error in Swift 6}}
     _ = \Door.[0] // expected-error{{cannot form key path to actor-isolated subscript 'subscript(_:)'}}
-    _ = \Door.["hello"] // okay for now
+    _ = \Door.["hello"] // expected-warning {{cannot form key path to actor-isolated subscript 'subscript(_:)'; this is an error in Swift 6}}
 }

test/Concurrency/sendable_keypaths.swift

@@ -140,17 +140,62 @@ do {
 }
 
 // Global actor isolated properties.
-do {
+func testGlobalActorIsolatedReferences() {
   @MainActor struct Isolated {
     var data: Int = 42
     subscript(v: Int) -> Bool { false }
   }
 
   let dataKP = \Isolated.data
+  // expected-warning@-1 {{cannot form key path to actor-isolated property 'data'; this is an error in Swift 6}}
   let subscriptKP = \Isolated.[42]
+  // expected-warning@-1 {{cannot form key path to actor-isolated subscript 'subscript(_:)'; this is an error in Swift 6}}
 
   let _: KeyPath<Isolated, Int> & Sendable = dataKP
   // expected-warning@-1 {{type 'WritableKeyPath<Isolated, Int>' does not conform to the 'Sendable' protocol}}
   let _: KeyPath<Isolated, Bool> & Sendable = subscriptKP
   // expected-warning@-1 {{type 'KeyPath<Isolated, Bool>' does not conform to the 'Sendable' protocol}}
+
+  func testNonIsolated() {
+    _ = \Isolated.data
+    // expected-warning@-1 {{cannot form key path to actor-isolated property 'data'; this is an error in Swift 6}}
+  }
+
+  @MainActor func testIsolated() {
+    _ = \Isolated.data // Ok
+  }
+}
+
+@available(SwiftStdlib 5.1, *)
+actor SomeActor {
+}
+
+@available(SwiftStdlib 5.1, *)
+@globalActor
+actor GlobalActor {
+  static let shared: SomeActor = SomeActor()
+}
+
+@available(SwiftStdlib 5.1, *)
+func testReferencesToDifferentGlobalActorIsolatedMembers() {
+  struct Info {
+    @MainActor var name: String  { "" }
+  }
+
+  struct Isolated {
+    @GlobalActor var info: Info { Info() }
+  }
+
+  @MainActor func testIsolatedToMain() {
+    _ = \Info.name // Ok
+    _ = \Isolated.info.name
+    // expected-warning@-1 {{cannot form key path to actor-isolated property 'info'; this is an error in Swift 6}}
+  }
+
+  @GlobalActor func testIsolatedToCustom() {
+    _ = \Info.name // Ok
+    // expected-warning@-1 {{cannot form key path to actor-isolated property 'name'; this is an error in Swift 6}}
+    _ = \Isolated.info.name
+    // expected-warning@-1 {{cannot form key path to actor-isolated property 'name'; this is an error in Swift 6}}
+  }
 }