[Distributed] Decl: Add a new distributed-thunk bit

The flag is used to distinguish between regular functions/accessors
and synthesized distributed thunks.

Author: xedin

include/swift/AST/Decl.h

@@ -412,7 +412,7 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
   SWIFT_INLINE_BITFIELD(SubscriptDecl, VarDecl, 2,
     StaticSpelling : 2
   );
-  SWIFT_INLINE_BITFIELD(AbstractFunctionDecl, ValueDecl, 3+2+8+1+1+1+1+1+1,
+  SWIFT_INLINE_BITFIELD(AbstractFunctionDecl, ValueDecl, 3+2+8+1+1+1+1+1+1+1,
     /// \see AbstractFunctionDecl::BodyKind
     BodyKind : 3,
 
@@ -439,7 +439,11 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
 
     /// Whether peeking into this function detected nested type declarations.
     /// This is set when skipping over the decl at parsing.
-    HasNestedTypeDeclarations : 1
+    HasNestedTypeDeclarations : 1,
+
+    /// Whether this function is a distributed thunk for a distributed
+    /// function or computed property.
+    DistributedThunk: 1
   );
 
   SWIFT_INLINE_BITFIELD(FuncDecl, AbstractFunctionDecl, 1+1+2+1+1+2+1,
@@ -6335,6 +6339,7 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
     Bits.AbstractFunctionDecl.Throws = Throws;
     Bits.AbstractFunctionDecl.HasSingleExpressionBody = false;
     Bits.AbstractFunctionDecl.HasNestedTypeDeclarations = false;
+    Bits.AbstractFunctionDecl.DistributedThunk = false;
   }
 
   void setBodyKind(BodyKind K) {
@@ -6433,6 +6438,16 @@ class AbstractFunctionDecl : public GenericContext, public ValueDecl {
   /// Returns 'true' if the function is distributed.
   bool isDistributed() const;
 
+  /// Is this a thunk function used to access a distributed method
+  /// or computed property outside of its actor isolation context?
+  bool isDistributedThunk() const {
+    return Bits.AbstractFunctionDecl.DistributedThunk;
+  }
+
+  void setDistributedThunk(bool isThunk) {
+    Bits.AbstractFunctionDecl.DistributedThunk = isThunk;
+  }
+
   /// For a 'distributed' target (func or computed property),
   /// get the 'thunk' responsible for performing the 'remoteCall'.
   ///

lib/AST/ASTDumper.cpp

@@ -878,6 +878,9 @@ namespace {
       if (D->isDistributed()) {
         PrintWithColorRAII(OS, ExprModifierColor) << " distributed";
       }
+      if (D->isDistributedThunk()) {
+        PrintWithColorRAII(OS, ExprModifierColor) << " distributed-thunk";
+      }
 
       if (auto fac = D->getForeignAsyncConvention()) {
         OS << " foreign_async=";

lib/Sema/CodeSynthesisDistributedActor.cpp

@@ -731,6 +731,7 @@ static FuncDecl *createDistributedThunkFunction(FuncDecl *func) {
       genericParamList, params,
       func->getResultInterfaceType(), DC);
   thunk->setSynthesized(true);
+  thunk->setDistributedThunk(true);
   thunk->getAttrs().add(new (C) NonisolatedAttr(/*isImplicit=*/true));
 
   if (isa<ClassDecl>(DC))

lib/Sema/TypeCheckDeclOverride.cpp

@@ -1612,7 +1612,6 @@ namespace  {
 
     UNINTERESTING_ATTR(UnsafeInheritExecutor)
     UNINTERESTING_ATTR(CompilerInitialized)
-
 #undef UNINTERESTING_ATTR
 
     void visitAvailableAttr(AvailableAttr *attr) {

lib/Serialization/Deserialization.cpp

@@ -3320,6 +3320,7 @@ class DeclDeserializer {
     bool overriddenAffectsABI, needsNewVTableEntry, isTransparent;
     DeclID opaqueReturnTypeID;
     bool isUserAccessible;
+    bool isDistributedThunk;
     ArrayRef<uint64_t> nameAndDependencyIDs;
 
     if (!isAccessor) {
@@ -3338,6 +3339,7 @@ class DeclDeserializer {
                                           needsNewVTableEntry,
                                           opaqueReturnTypeID,
                                           isUserAccessible,
+                                          isDistributedThunk,
                                           nameAndDependencyIDs);
     } else {
       decls_block::AccessorLayout::readRecord(scratch, contextID, isImplicit,
@@ -3355,6 +3357,7 @@ class DeclDeserializer {
                                               rawAccessLevel,
                                               needsNewVTableEntry,
                                               isTransparent,
+                                              isDistributedThunk,
                                               nameAndDependencyIDs);
     }
 
@@ -3531,6 +3534,8 @@ class DeclDeserializer {
     if (!isAccessor)
       fn->setUserAccessible(isUserAccessible);
 
+    fn->setDistributedThunk(isDistributedThunk);
+
     return fn;
   }
 

lib/Serialization/ModuleFormat.h

@@ -58,7 +58,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 695; // existential Any and AnyObject
+const uint16_t SWIFTMODULE_VERSION_MINOR = 696; // `distributed thunk` bit on `AbstractFunctionDecl`
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -1451,6 +1451,7 @@ namespace decls_block {
     BCFixed<1>,   // requires a new vtable slot
     DeclIDField,  // opaque result type decl
     BCFixed<1>,   // isUserAccessible?
+    BCFixed<1>,   // is distributed thunk
     BCArray<IdentifierIDField> // name components,
                                // followed by TypeID dependencies
     // The record is trailed by:
@@ -1502,6 +1503,7 @@ namespace decls_block {
     AccessLevelField, // access level
     BCFixed<1>,   // requires a new vtable slot
     BCFixed<1>,   // is transparent
+    BCFixed<1>,   // is distributed thunk
     BCArray<IdentifierIDField> // name components,
                                // followed by TypeID dependencies
     // The record is trailed by:

lib/Serialization/Serialization.cpp

@@ -3891,6 +3891,7 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
                            fn->needsNewVTableEntry(),
                            S.addDeclRef(fn->getOpaqueResultTypeDecl()),
                            fn->isUserAccessible(),
+                           fn->isDistributedThunk(),
                            nameComponentsAndDependencies);
 
     writeGenericParams(fn->getGenericParams());
@@ -4002,6 +4003,7 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
                                rawAccessLevel,
                                fn->needsNewVTableEntry(),
                                fn->isTransparent(),
+                               fn->isDistributedThunk(),
                                dependencies);
 
     writeGenericParams(fn->getGenericParams());