[Distributed] Synthesize thunks for distributed computed properties

Author: xedin

include/swift/AST/Decl.h

@@ -5355,6 +5355,10 @@ class VarDecl : public AbstractStorageDecl {
   /// Does this have a 'distributed' modifier?
   bool isDistributed() const;
 
+  /// Return a distributed thunk if this computed property is marked as
+  /// 'distributed' and and nullptr otherwise.
+  FuncDecl *getDistributedThunk() const;
+
   /// Is this var known to be a "local" distributed actor,
   /// if so the implicit throwing ans some isolation checks can be skipped.
   bool isKnownToBeLocal() const;

include/swift/AST/TypeCheckRequests.h

@@ -1237,17 +1237,20 @@ class GetDistributedRemoteCallArgumentInitFunctionRequest :
 ///
 /// The thunk is responsible for invoking 'remoteCall' when invoked on a remote
 /// 'distributed actor'.
-class GetDistributedThunkRequest :
-    public SimpleRequest<GetDistributedThunkRequest,
-                         FuncDecl *(AbstractFunctionDecl *),
-                         RequestFlags::Cached> {
+class GetDistributedThunkRequest
+    : public SimpleRequest<
+          GetDistributedThunkRequest,
+          FuncDecl *(llvm::PointerUnion<VarDecl *, AbstractFunctionDecl *>),
+          RequestFlags::Cached> {
+  using Originator = llvm::PointerUnion<VarDecl *, AbstractFunctionDecl *>;
+
 public:
   using SimpleRequest::SimpleRequest;
 
 private:
   friend SimpleRequest;
 
-  FuncDecl *evaluate(Evaluator &evaluator, AbstractFunctionDecl *distributedFunc) const;
+  FuncDecl *evaluate(Evaluator &evaluator, Originator originator) const;
 
 public:
   // Caching

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -127,7 +127,7 @@ SWIFT_REQUEST(TypeChecker, GetDistributedTargetInvocationResultHandlerOnReturnFu
               AbstractFunctionDecl *(NominalTypeDecl *),
               Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, GetDistributedThunkRequest,
-              FuncDecl *(AbstractFunctionDecl *),
+              FuncDecl *(llvm::PointerUnion<VarDecl *, AbstractFunctionDecl *>),
               Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, GetDistributedActorIDPropertyRequest,
               VarDecl *(NominalTypeDecl *),

lib/AST/DistributedDecl.cpp

@@ -1333,6 +1333,20 @@ AbstractFunctionDecl *ASTContext::getRemoteCallOnDistributedActorSystem(
 /********************** Distributed Actor Properties **************************/
 /******************************************************************************/
 
+FuncDecl *VarDecl::getDistributedThunk() const {
+  if (!isDistributed())
+    return nullptr;
+
+  // Only get-only 'distributed' computed properties are considered valid.
+  if (isStatic() || isLet() || hasStorageOrWrapsStorage() ||
+      getWriteImpl() != swift::WriteImplKind::Immutable)
+    return nullptr;
+
+  auto mutableThis = const_cast<VarDecl *>(this);
+  return evaluateOrDefault(getASTContext().evaluator,
+                           GetDistributedThunkRequest{mutableThis}, nullptr);
+}
+
 FuncDecl*
 AbstractFunctionDecl::getDistributedThunk() const {
   if (!isDistributed())

lib/Sema/CodeSynthesisDistributedActor.cpp

@@ -681,7 +681,18 @@ static FuncDecl *createDistributedThunkFunction(FuncDecl *func) {
   assert(systemTy &&
          "Thunk synthesis must have concrete actor system type available");
 
-  DeclName thunkName = func->getName();
+  DeclName thunkName;
+
+  // Since accessors don't have names, let's generate one based on
+  // the computed property.
+  if (auto *accessor = dyn_cast<AccessorDecl>(func)) {
+    auto *var = accessor->getStorage();
+    thunkName = DeclName(C, var->getBaseName(),
+                         /*argumentNames=*/ArrayRef<Identifier>());
+  } else {
+    // Let's use the name of a 'distributed func'
+    thunkName = func->getName();
+  }
 
   // --- Prepare generic parameters
   GenericParamList *genericParamList = nullptr;
@@ -811,10 +822,21 @@ addDistributedActorCodableConformance(
 /*********************** SYNTHESIS ENTRY POINTS *******************************/
 /******************************************************************************/
 
-FuncDecl *GetDistributedThunkRequest::evaluate(
-    Evaluator &evaluator, AbstractFunctionDecl *distributedTarget) const {
-  if (!distributedTarget->isDistributed())
-    return nullptr;
+FuncDecl *GetDistributedThunkRequest::evaluate(Evaluator &evaluator,
+                                               Originator originator) const {
+  AbstractFunctionDecl *distributedTarget = nullptr;
+  if (auto *var = originator.dyn_cast<VarDecl *>()) {
+    if (!var->isDistributed())
+      return nullptr;
+
+    distributedTarget = var->getAccessor(AccessorKind::Get);
+  } else {
+    distributedTarget = originator.get<AbstractFunctionDecl *>();
+    if (!distributedTarget->isDistributed())
+      return nullptr;
+  }
+
+  assert(distributedTarget);
 
   auto &C = distributedTarget->getASTContext();
   auto DC = distributedTarget->getDeclContext();

lib/Sema/TypeCheckDistributed.cpp

@@ -483,7 +483,12 @@ bool swift::checkDistributedFunction(AbstractFunctionDecl *func) {
 
 bool CheckDistributedFunctionRequest::evaluate(
     Evaluator &evaluator, AbstractFunctionDecl *func) const {
-  assert(func->isDistributed());
+  if (auto *accessor = dyn_cast<AccessorDecl>(func)) {
+    auto *var = cast<VarDecl>(accessor->getStorage());
+    assert(var->isDistributed() && accessor->isGetter());
+  } else {
+    assert(func->isDistributed());
+  }
 
   auto &C = func->getASTContext();
   auto DC = func->getDeclContext();
@@ -654,6 +659,18 @@ void TypeChecker::checkDistributedActor(SourceFile *SF, NominalTypeDecl *nominal
   (void)nominal->getDefaultInitializer();
 
   for (auto member : nominal->getMembers()) {
+    // A distributed computed property needs to have a thunk for
+    // its getter accessor.
+    if (auto *var = dyn_cast<VarDecl>(member)) {
+      if (!var->isDistributed())
+        continue;
+
+      if (auto thunk = var->getDistributedThunk())
+        SF->DelayedFunctions.push_back(thunk);
+
+      continue;
+    }
+
     // --- Ensure all thunks
     if (auto func = dyn_cast<AbstractFunctionDecl>(member)) {
       if (!func->isDistributed())