DistributedActors: Fix another upcoming request cycle

Author: slavapestov

lib/Sema/DerivedConformance/DerivedConformance.cpp

@@ -100,7 +100,7 @@ bool DerivedConformance::derivesProtocolConformance(DeclContext *DC,
   if (*derivableKind == KnownDerivableProtocolKind::DistributedActor)
     return canDeriveDistributedActor(Nominal, DC);
   if (*derivableKind == KnownDerivableProtocolKind::DistributedActorSystem)
-    return canDeriveDistributedActorSystem(Nominal, DC);
+    return canDeriveDistributedActorSystem(Conformance);
 
   if (*derivableKind == KnownDerivableProtocolKind::AdditiveArithmetic)
     return canDeriveAdditiveArithmetic(Nominal, DC);

lib/Sema/DerivedConformance/DerivedConformance.h

@@ -338,8 +338,8 @@ class DerivedConformance {
                                         DeclContext *dc);
 
   /// Whether we can derive the given DistributedActorSystem requirements.
-  static bool canDeriveDistributedActorSystem(NominalTypeDecl *nominal,
-                                              DeclContext *dc);
+  static bool canDeriveDistributedActorSystem(
+      NormalProtocolConformance *conformance);
 
   /// Derive a 'DistributedActor' requirement for an distributed actor.
   ///

lib/Sema/DerivedConformance/DerivedConformanceDistributedActor.cpp

@@ -54,18 +54,26 @@ bool DerivedConformance::canDeriveDistributedActor(
 }
 
 bool DerivedConformance::canDeriveDistributedActorSystem(
-    NominalTypeDecl *nominal, DeclContext *dc) {
-  auto &C = nominal->getASTContext();
+    NormalProtocolConformance *conformance) {
+  auto &ctx = conformance->getDeclContext()->getASTContext();
 
-  // Make sure ad-hoc requirements that we'll use in synthesis are present, before we try to use them.
-  // This leads to better error reporting because we already have errors happening (missing witnesses).
-  if (auto handlerType = getDistributedActorSystemResultHandlerType(nominal)) {
-    if (!getOnReturnOnDistributedTargetInvocationResultHandler(
-            handlerType->getAnyNominal()))
-      return false;
-  }
+  if (!ctx.getLoadedModule(ctx.Id_Distributed))
+    return false;
+
+  auto *assocType = conformance->getProtocol()->getAssociatedType(
+      ctx.Id_ResultHandler);
+  if (!assocType)
+    return false;
+
+  if (!conformance->hasTypeWitness(assocType))
+    return false;
+
+  auto handlerType = conformance->getTypeWitness(assocType);
+  if (!getOnReturnOnDistributedTargetInvocationResultHandler(
+          handlerType->getAnyNominal()))
+    return false;
 
-  return C.getLoadedModule(C.Id_Distributed);
+  return true;
 }
 
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