Introduce class TypeRef in the VM to fully support recursive types.

runtime/vm/raw_object.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/globals.h"
 #include "vm/token.h"
@@ skipping 32 matching lines @@
   V(MegamorphicCache)                                                          \
   V(SubtypeTestCache)                                                          \
   V(Error)                                                                     \
     V(ApiError)                                                                \
     V(LanguageError)                                                           \
     V(UnhandledException)                                                      \
     V(UnwindError)                                                             \
   V(Instance)                                                                  \
     V(AbstractType)                                                            \
       V(Type)                                                                  \
+      V(TypeRef)                                                               \
       V(TypeParameter)                                                         \
       V(BoundedType)                                                           \
       V(MixinAppType)                                                          \
     V(Number)                                                                  \
       V(Integer)                                                               \
         V(Smi)                                                                 \
         V(Mint)                                                                \
         V(Bigint)                                                              \
       V(Double)                                                                \
     V(Bool)                                                                    \
@@ skipping 1108 matching lines @@
   RawAbstractTypeArguments* arguments_;
   RawLanguageError* error_;  // Error object if type is malformed or malbounded.
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&ptr()->error_);
   }
   intptr_t token_pos_;
   int8_t type_state_;
 };
 
 
+class RawTypeRef : public RawAbstractType {
+ private:
+  RAW_HEAP_OBJECT_IMPLEMENTATION(TypeRef);
+
+  RawObject** from() {
+    return reinterpret_cast<RawObject**>(&ptr()->type_);
+  }
+  RawAbstractType* type_;  // The referenced type.
+  RawObject** to() {
+    return reinterpret_cast<RawObject**>(&ptr()->type_);
+  }
+  bool is_being_checked_;  // Transient field, not snapshotted.
+};
+
+
 class RawTypeParameter : public RawAbstractType {
  private:
   RAW_HEAP_OBJECT_IMPLEMENTATION(TypeParameter);
 
   RawObject** from() {
     return reinterpret_cast<RawObject**>(&ptr()->parameterized_class_);
   }
   RawClass* parameterized_class_;
   RawString* name_;
   RawAbstractType* bound_;  // ObjectType if no explicit bound specified.
@@ skipping 10 matching lines @@
 
   RawObject** from() {
     return reinterpret_cast<RawObject**>(&ptr()->type_);
   }
   RawAbstractType* type_;
   RawAbstractType* bound_;
   RawTypeParameter* type_parameter_;  // For more detailed error reporting.
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&ptr()->type_parameter_);
   }
-  bool is_being_checked_;
+  bool is_being_checked_;  // Transient field, not snapshotted.
 };
 
 
 class RawMixinAppType : public RawAbstractType {
  private:
   RAW_HEAP_OBJECT_IMPLEMENTATION(MixinAppType);
 
   RawObject** from() {
     return reinterpret_cast<RawObject**>(&ptr()->super_type_);
   }
@@ skipping 509 matching lines @@
   // Make sure this is updated when new TypedData types are added.
   ASSERT(kTypedDataInt8ArrayViewCid == kTypedDataInt8ArrayCid + 13);
   ASSERT(kExternalTypedDataInt8ArrayCid == kTypedDataInt8ArrayViewCid + 14);
   ASSERT(kNullCid == kExternalTypedDataInt8ArrayCid + 13);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_