Implement reflection support for Symbolic Extended Existential types.

This patch adds a new SymbolicExtendedExistentialTypeRef kind, and
wires it up in TypeDecoder, TypeRefBuilder, TypeLowering, and
ASTDemangler.

This is tested indirectly via the matching LLDB commit.

Author: adrian-prantl

include/swift/Demangling/TypeDecoder.h

@@ -573,6 +573,43 @@ void decodeRequirement(
   }
 }
 
+/// Extract the protocol and requirement nodes from a shape symbol.
+static inline std::pair<NodePointer, NodePointer>
+decodeShape(NodePointer Node) {
+  if (!Node || Node->getKind() != Node::Kind::Global ||
+      Node->getNumChildren() != 1)
+    return {nullptr, nullptr};
+  Node = Node->getChild(0);
+  if (Node && (Node->getKind() == Node::Kind::Uniquable) &&
+      Node->getNumChildren() == 1)
+    Node = Node->getChild(0);
+  if (!Node || Node->getKind() != Node::Kind::ExtendedExistentialTypeShape ||
+      Node->getNumChildren() != 2)
+    return {nullptr, nullptr};
+  Node = Node->getChild(1);
+  if (!Node || Node->getKind() != Node::Kind::Type ||
+      Node->getNumChildren() != 1)
+    return {nullptr, nullptr};
+  Node = Node->getChild(0);
+  if (!Node || Node->getKind() != Node::Kind::ConstrainedExistential ||
+      Node->getNumChildren() != 2)
+    return {nullptr, nullptr};
+  NodePointer Requirements = Node->getChild(1);
+  if (!Requirements || Requirements->getKind() !=
+                           Node::Kind::ConstrainedExistentialRequirementList)
+    return {nullptr, nullptr};
+
+  Node = Node->getChild(0);
+  if (!Node || Node->getKind() != Node::Kind::Type ||
+      Node->getNumChildren() != 1)
+    return {nullptr, nullptr};
+  NodePointer Protocol = Node;
+  if (!Protocol)
+    return {nullptr, nullptr};
+
+  return {Protocol, Requirements};
+}
+
 #define MAKE_NODE_TYPE_ERROR(Node, Fmt, ...)                                   \
   TYPE_LOOKUP_ERROR_FMT("TypeDecoder.h:%u: Node kind %u \"%.*s\" - " Fmt,      \
                         __LINE__, (unsigned)Node->getKind(),                   \

include/swift/Remote/MetadataReader.h

@@ -509,8 +509,8 @@ class MetadataReader {
         // The symbolic reference points at a non-unique extended
         // existential type shape.
         return dem.createNode(
-                          Node::Kind::NonUniqueExtendedExistentialTypeShapeSymbolicReference,
-                          resolved.getResolvedAddress().getAddressData());
+            Node::Kind::NonUniqueExtendedExistentialTypeShapeSymbolicReference,
+            resolved.getResolvedAddress().getAddressData());
       }
       case Demangle::SymbolicReferenceKind::ObjectiveCProtocol: {
         // 'resolved' points to a struct of two relative addresses.
@@ -886,6 +886,74 @@ class MetadataReader {
     return resolver.swiftProtocol(Demangled);
   }
 
+  BuiltType readTypeFromShape(
+      RemoteAbsolutePointer shapeAddress,
+      std::function<std::optional<std::vector<BuiltType>>(unsigned)> getArgs) {
+    StoredPointer addr = shapeAddress.getResolvedAddress().getAddressData();
+    ShapeRef Shape = readShape(addr);
+    if (!Shape)
+      return BuiltType();
+
+    assert(Shape->hasGeneralizationSignature());
+    auto builtArgs = getArgs(Shape->getGenSigArgumentLayoutSizeInWords());
+
+    // Pull out the existential type from the mangled type name.
+    Demangler dem;
+    auto mangledExistentialAddr =
+        resolveRelativeField(Shape, Shape->ExistentialType);
+    auto node = readMangledName(RemoteAddress(mangledExistentialAddr),
+                                MangledNameKind::Type, dem);
+    if (!node)
+      return BuiltType();
+
+    BuiltType builtProto = decodeMangledType(node).getType();
+    if (!builtProto)
+      return BuiltType();
+
+    if (builtArgs) {
+      // Build up a substitution map for the generalized signature.
+      BuiltGenericSignature sig =
+          decodeRuntimeGenericSignature(Shape,
+                                        Shape->getGeneralizationSignature())
+              .getType();
+      if (!sig)
+        return BuiltType();
+
+      BuiltSubstitutionMap subst =
+          Builder.createSubstitutionMap(sig, *builtArgs);
+      if (subst.empty())
+        return BuiltType();
+
+      builtProto = Builder.subst(builtProto, subst);
+      if (!builtProto)
+        return BuiltType();
+    }
+
+    // Read the type expression to build up any remaining layers of
+    // existential metatype.
+    if (Shape->Flags.hasTypeExpression()) {
+      Demangler dem;
+
+      // Read the mangled name.
+      auto mangledContextName = Shape->getTypeExpression();
+      auto mangledNameAddress =
+          resolveRelativeField(Shape, mangledContextName->name);
+      auto node = readMangledName(RemoteAddress(mangledNameAddress),
+                                  MangledNameKind::Type, dem);
+      if (!node)
+        return BuiltType();
+
+      while (node->getKind() == Demangle::Node::Kind::Type &&
+             node->getNumChildren() &&
+             node->getChild(0)->getKind() == Demangle::Node::Kind::Metatype &&
+             node->getChild(0)->getNumChildren()) {
+        builtProto = Builder.createExistentialMetatypeType(builtProto);
+        node = node->getChild(0)->getChild(0);
+      }
+    }
+    return builtProto;
+  }
+
   /// Given a remote pointer to metadata, attempt to turn it into a type.
   BuiltType
   readTypeFromMetadata(StoredPointer MetadataAddress,
@@ -1081,79 +1149,25 @@ class MetadataReader {
     }
     case MetadataKind::ExtendedExistential: {
       auto Exist = cast<TargetExtendedExistentialTypeMetadata<Runtime>>(Meta);
-
       // Read the shape for this existential.
       StoredPointer shapeAddress = stripSignedPointer(Exist->Shape);
-      ShapeRef Shape = readShape(shapeAddress);
-      if (!Shape)
-        return BuiltType();
-
-      const unsigned shapeArgumentCount
-          = Shape->getGenSigArgumentLayoutSizeInWords();
-      // Pull out the arguments to the generalization signature.
-      assert(Shape->hasGeneralizationSignature());
-      std::vector<BuiltType> builtArgs;
-      for (unsigned i = 0; i < shapeArgumentCount; ++i) {
-        auto remoteArg = Exist->getGeneralizationArguments()[i];
-        auto builtArg = readTypeFromMetadata(remoteArg, false, recursion_limit);
-        if (!builtArg)
-          return BuiltType();
-        builtArgs.push_back(builtArg);
-      }
-
-      // Pull out the existential type from the mangled type name.
-      Demangler dem;
-      auto mangledExistentialAddr =
-          resolveRelativeField(Shape, Shape->ExistentialType);
-      auto node = readMangledName(RemoteAddress(mangledExistentialAddr),
-                                  MangledNameKind::Type, dem);
-      if (!node)
-        return BuiltType();
-
-      BuiltType builtProto = decodeMangledType(node).getType();
-      if (!builtProto)
-        return BuiltType();
-
-      // Build up a substitution map for the generalized signature.
-      BuiltGenericSignature sig =
-          decodeRuntimeGenericSignature(Shape,
-                                        Shape->getGeneralizationSignature())
-              .getType();
-      if (!sig)
-        return BuiltType();
-
-      BuiltSubstitutionMap subst =
-          Builder.createSubstitutionMap(sig, builtArgs);
-      if (subst.empty())
-        return BuiltType();
-
-      builtProto = Builder.subst(builtProto, subst);
-      if (!builtProto)
-        return BuiltType();
-
-      // Read the type expression to build up any remaining layers of
-      // existential metatype.
-      if (Shape->Flags.hasTypeExpression()) {
-        Demangler dem;
-
-        // Read the mangled name.
-        auto mangledContextName = Shape->getTypeExpression();
-        auto mangledNameAddress =
-            resolveRelativeField(Shape, mangledContextName->name);
-        auto node = readMangledName(RemoteAddress(mangledNameAddress),
-                                    MangledNameKind::Type, dem);
-        if (!node)
-          return BuiltType();
-
-        while (node->getKind() == Demangle::Node::Kind::Type &&
-               node->getNumChildren() &&
-               node->getChild(0)->getKind() == Demangle::Node::Kind::Metatype &&
-               node->getChild(0)->getNumChildren()) {
-          builtProto = Builder.createExistentialMetatypeType(builtProto);
-          node = node->getChild(0)->getChild(0);
-        }
-      }
 
+      auto builtProto = readTypeFromShape(
+          RemoteAddress(shapeAddress),
+          [&](unsigned shapeArgumentCount)
+              -> std::optional<std::vector<BuiltType>> {
+            // Pull out the arguments to the generalization signature.
+            std::vector<BuiltType> builtArgs;
+            for (unsigned i = 0; i < shapeArgumentCount; ++i) {
+              auto remoteArg = Exist->getGeneralizationArguments()[i];
+              auto builtArg =
+                  readTypeFromMetadata(remoteArg, false, recursion_limit);
+              if (!builtArg)
+                return std::nullopt;
+              builtArgs.push_back(builtArg);
+            }
+            return builtArgs;
+          });
       TypeCache[TypeCacheKey] = builtProto;
       return builtProto;
     }
@@ -1366,69 +1380,60 @@ class MetadataReader {
       if (address.getOffset() == 0)
         return ParentContextDescriptorRef(address.getSymbol());
     }
-    
+
     return ParentContextDescriptorRef(
-          readContextDescriptor(address.getResolvedAddress().getAddressData()));
+        readContextDescriptor(address.getResolvedAddress().getAddressData()));
   }
 
-  ShapeRef
-  readShape(StoredPointer address) {
+  ShapeRef readShape(StoredPointer address) {
     if (address == 0)
       return nullptr;
 
+    using ShapeHeader = TargetExtendedExistentialTypeShape<Runtime>;
     auto cached = ShapeCache.find(address);
     if (cached != ShapeCache.end())
-      return ShapeRef(address,
-        reinterpret_cast<const TargetExtendedExistentialTypeShape<Runtime> *>(
-            cached->second.get()));
-
-    ExtendedExistentialTypeShapeFlags flags;
-    if (!Reader->readBytes(RemoteAddress(address), (uint8_t*)&flags,
-                           sizeof(flags)))
-      return nullptr;
+      return ShapeRef(
+          address, reinterpret_cast<const ShapeHeader *>(cached->second.get()));
 
-    // Read the size of the requirement signature.
-    uint64_t reqSigGenericSize = 0;
-    uint64_t genericHeaderSize = sizeof(GenericContextDescriptorHeader);
+    uint64_t descriptorSize;
     {
-      GenericContextDescriptorHeader header;
-      auto headerAddr = address + sizeof(flags);
-
-      if (!Reader->readBytes(RemoteAddress(headerAddr),
-                             (uint8_t*)&header, sizeof(header)))
+      auto readResult =
+          Reader->readBytes(RemoteAddress(address), sizeof(ShapeHeader));
+      if (!readResult)
         return nullptr;
-
-      reqSigGenericSize = reqSigGenericSize
-        + (header.NumParams + 3u & ~3u)
-        + header.NumRequirements
-          * sizeof(TargetGenericRequirementDescriptor<Runtime>);
-    }
-    uint64_t typeExprSize = flags.hasTypeExpression() ? sizeof(StoredPointer) : 0;
-    uint64_t suggestedVWSize = flags.hasSuggestedValueWitnesses() ? sizeof(StoredPointer) : 0;
-
-    uint64_t size = sizeof(ExtendedExistentialTypeShapeFlags) +
-                    sizeof(TargetRelativeDirectPointer<Runtime, const char,
-                                                       /*nullable*/ false>) +
-                    genericHeaderSize + typeExprSize + suggestedVWSize +
-                    reqSigGenericSize;
-    if (size > MaxMetadataSize)
+      auto shapeHeader =
+          reinterpret_cast<const ShapeHeader *>(readResult.get());
+
+      // Read the size of the requirement signature.
+      uint64_t reqSigGenericSize = 0;
+      auto flags = shapeHeader->Flags;
+      auto &reqSigHeader = shapeHeader->ReqSigHeader;
+      reqSigGenericSize =
+          reqSigGenericSize + (reqSigHeader.NumParams + 3u & ~3u) +
+          reqSigHeader.NumRequirements *
+              sizeof(TargetGenericRequirementDescriptor<Runtime>);
+      uint64_t typeExprSize =
+          flags.hasTypeExpression() ? sizeof(StoredPointer) : 0;
+      uint64_t suggestedVWSize =
+          flags.hasSuggestedValueWitnesses() ? sizeof(StoredPointer) : 0;
+
+      descriptorSize = sizeof(shapeHeader) + typeExprSize + suggestedVWSize +
+                       reqSigGenericSize;
+    }
+    if (descriptorSize > MaxMetadataSize)
       return nullptr;
-    auto readResult = Reader->readBytes(RemoteAddress(address), size);
+    auto readResult = Reader->readBytes(RemoteAddress(address), descriptorSize);
     if (!readResult)
       return nullptr;
 
-    auto descriptor =
-        reinterpret_cast<const TargetExtendedExistentialTypeShape<Runtime> *>(
-            readResult.get());
+    auto descriptor = reinterpret_cast<const ShapeHeader *>(readResult.get());
 
-    ShapeCache.insert(
-        std::make_pair(address, std::move(readResult)));
+    ShapeCache.insert(std::make_pair(address, std::move(readResult)));
     return ShapeRef(address, descriptor);
   }
 
   /// Given the address of a context descriptor, attempt to read it.
-  ContextDescriptorRef
-  readContextDescriptor(StoredPointer address) {
+  ContextDescriptorRef readContextDescriptor(StoredPointer address) {
     if (address == 0)
       return nullptr;
 

include/swift/RemoteInspection/TypeRef.h

@@ -731,6 +731,64 @@ class ConstrainedExistentialTypeRef final : public TypeRef {
   }
 };
 
+class SymbolicExtendedExistentialTypeRef final : public TypeRef {
+  const ProtocolCompositionTypeRef *Protocol;
+  std::vector<TypeRefRequirement> Requirements;
+  std::vector<const TypeRef *> Arguments;
+  ExtendedExistentialTypeShapeFlags Flags;
+
+  static TypeRefID Profile(const ProtocolCompositionTypeRef *Protocol,
+                           llvm::ArrayRef<TypeRefRequirement> Requirements,
+                           llvm::ArrayRef<const TypeRef *> Arguments,
+                           ExtendedExistentialTypeShapeFlags Flags) {
+    TypeRefID ID;
+    ID.addPointer(Protocol);
+    for (auto reqt : Requirements) {
+      ID.addPointer(reqt.getFirstType());
+      if (reqt.getKind() != RequirementKind::Layout)
+        ID.addPointer(reqt.getSecondType());
+      else
+        ID.addInteger(
+            unsigned(0)); // FIXME: Layout constraints aren't implemented yet
+      ID.addInteger(unsigned(reqt.getKind()));
+    }
+
+    for (auto &Arg : Arguments)
+      ID.addPointer(Arg);
+    return ID;
+  }
+
+public:
+  SymbolicExtendedExistentialTypeRef(
+      const ProtocolCompositionTypeRef *Protocol,
+      llvm::ArrayRef<TypeRefRequirement> Requirements,
+      llvm::ArrayRef<const TypeRef *> Args,
+      ExtendedExistentialTypeShapeFlags Flags)
+      : TypeRef(TypeRefKind::SymbolicExtendedExistential), Protocol(Protocol),
+        Requirements(Requirements), Arguments(Args), Flags(Flags) {}
+
+  template <typename Allocator>
+  static const SymbolicExtendedExistentialTypeRef *
+  create(Allocator &A, const ProtocolCompositionTypeRef *Protocol,
+         llvm::ArrayRef<TypeRefRequirement> Requirements,
+         llvm::ArrayRef<const TypeRef *> Args,
+         ExtendedExistentialTypeShapeFlags Flags) {
+    FIND_OR_CREATE_TYPEREF(A, SymbolicExtendedExistentialTypeRef, Protocol,
+                           Requirements, Args, Flags);
+  }
+
+  const ProtocolCompositionTypeRef *getProtocol() const { return Protocol; }
+  llvm::ArrayRef<TypeRefRequirement> getRequirements() const {
+    return Requirements;
+  }
+  llvm::ArrayRef<const TypeRef *> getArguments() const { return Arguments; }
+  ExtendedExistentialTypeShapeFlags getFlags() const { return Flags; }
+
+  static bool classof(const TypeRef *TR) {
+    return TR->getKind() == TypeRefKind::SymbolicExtendedExistential;
+  }
+};
+
 class MetatypeTypeRef final : public TypeRef {
   const TypeRef *InstanceType;
   bool WasAbstract;