[Distributed] Fix ActorSystem requests on protocols that conform to DistributedActor

Author: xedin

lib/AST/DistributedDecl.cpp

@@ -207,6 +207,23 @@ Type ASTContext::getAssociatedTypeOfDistributedSystemOfActor(
     return Type();
 
   auto module = actor->getParentModule();
+
+  // In case of protocol, let's find a concrete `ActorSystem`
+  if (auto *protocol = dyn_cast<ProtocolDecl>(actor)) {
+    auto signature = protocol->getGenericSignatureOfContext();
+
+    auto systemTy =
+        signature->getConcreteType(actorSystemDecl->getDeclaredInterfaceType());
+    if (!systemTy)
+      return Type();
+
+    auto conformance = module->lookupConformance(systemTy, actorSystemProtocol);
+    if (conformance.isInvalid())
+      return Type();
+
+    return conformance.getTypeWitnessByName(systemTy, member);
+  }
+
   Type selfType = actor->getSelfInterfaceType();
   auto conformance = module->lookupConformance(selfType, actorProtocol);
   Type dependentType = actorProtocol->getSelfInterfaceType();

test/Distributed/Runtime/distributed_actor_hop_to.swift

@@ -24,14 +24,14 @@ protocol LifecycleWatch: DistributedActor where ActorSystem == FakeRoundtripActo
 }
 
 extension LifecycleWatch {
-  func watch() async throws {
+  func watch<T: Codable>(x: Int, _ y: T) async throws {
     // nothing here
-    print("executed: \(#function)")
+    print("executed: \(#function) - x = \(x), y = \(y)")
   }
 
-  distributed func test() async throws {
+  distributed func test<T: Codable>(x: Int, _ y: T) async throws {
     print("executed: \(#function)")
-    try await self.watch()
+    try await self.watch(x: x, y)
     print("done executed: \(#function)")
   }
 }
@@ -42,11 +42,11 @@ distributed actor Worker: LifecycleWatch {
 @main struct Main {
   static func main() async {
     let worker: any LifecycleWatch = Worker(actorSystem: DefaultDistributedActorSystem())
-    try! await worker.test()
+    try! await worker.test(x: 42, "on protocol")
 
-    // CHECK: executed: test()
-    // CHECK: executed: watch()
-    // CHECK: done executed: test()
+    // CHECK: executed: test(x:_:)
+    // CHECK: executed: watch(x:_:) - x = 42, y = on protocol
+    // CHECK: done executed: test(x:_:)
 
     print("OK") // CHECK: OK
   }