Sema: Simplify IsDistributedActor same as #37798 (#37811)

Author: ktoso

include/swift/AST/Decl.h

@@ -3812,6 +3812,12 @@ class ClassDecl final : public NominalTypeDecl {
   /// Whether the class was explicitly declared with the `actor` keyword.
   bool isExplicitActor() const { return Bits.ClassDecl.IsActor; }
 
+  /// Whether the class was explicitly declared with the `distributed actor` keywords.
+  bool isExplicitDistributedActor() const {
+    return isExplicitActor() &&
+           getAttrs().hasAttribute<DistributedActorAttr>();
+  }
+
   /// Get the closest-to-root superclass that's an actor class.
   const ClassDecl *getRootActorClass() const;
 

lib/Sema/TypeCheckDistributed.cpp

@@ -33,32 +33,20 @@ using namespace swift;
 
 bool IsDistributedActorRequest::evaluate(
     Evaluator &evaluator, NominalTypeDecl *nominal) const {
-  // Protocols are actors if their `Self` type conforms to `DistributedActor`.
+  // Protocols are actors if they inherit from `DistributedActor`.
   if (auto protocol = dyn_cast<ProtocolDecl>(nominal)) {
-    // Simple case: we have the `DistributedActor` protocol itself.
-    if (protocol->isSpecificProtocol(KnownProtocolKind::DistributedActor))
-      return true;
-
-    auto actorProto = nominal->getASTContext().getProtocol(
-        KnownProtocolKind::DistributedActor);
-    if (!actorProto)
-      return false;
-
-    auto selfType = Type(protocol->getProtocolSelfType());
-    auto genericSig = protocol->getGenericSignature();
-    if (!genericSig)
-      return false;
-
-    return genericSig->requiresProtocol(selfType, actorProto);
+    auto &ctx = protocol->getASTContext();
+    auto *distributedActorProtocol = ctx.getProtocol(KnownProtocolKind::DistributedActor);
+    return (protocol == distributedActorProtocol ||
+            protocol->inheritsFrom(distributedActorProtocol));
   }
 
   // Class declarations are 'distributed actors' if they are declared with 'distributed actor'
-  if(!dyn_cast<ClassDecl>(nominal))
+  auto classDecl = dyn_cast<ClassDecl>(nominal);
+  if(!classDecl)
     return false;
 
-  auto distributedAttr = nominal->getAttrs()
-      .getAttribute<DistributedActorAttr>();
-  return distributedAttr != nullptr;
+  return classDecl->isExplicitDistributedActor();
 }
 
 bool IsDistributedFuncRequest::evaluate(