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

runtime/vm/snapshot.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_SNAPSHOT_H_
 #define VM_SNAPSHOT_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
@@ skipping 43 matching lines @@
 class RawLiteralToken;
 class RawMint;
 class RawObject;
 class RawOneByteString;
 class RawPatchClass;
 class RawScript;
 class RawSmi;
 class RawStacktrace;
 class RawTokenStream;
 class RawType;
+class RawTypeRef;
 class RawTypeParameter;
 class RawTypeArguments;
 class RawTwoByteString;
 class RawUnresolvedClass;
 class String;
 class TokenStream;
 class UnhandledException;
 
 // Serialized object header encoding is as follows:
 // - Smi: the Smi value is written as is (last bit is not tagged).
@@ skipping 175 matching lines @@
   RawTwoByteString* NewTwoByteString(intptr_t len);
   RawTypeArguments* NewTypeArguments(intptr_t len);
   RawTokenStream* NewTokenStream(intptr_t len);
   RawContext* NewContext(intptr_t num_variables);
   RawClass* NewClass(intptr_t class_id);
   RawMint* NewMint(int64_t value);
   RawBigint* NewBigint(const char* hex_string);
   RawDouble* NewDouble(double value);
   RawUnresolvedClass* NewUnresolvedClass();
   RawType* NewType();
+  RawTypeRef* NewTypeRef();
   RawTypeParameter* NewTypeParameter();
   RawBoundedType* NewBoundedType();
   RawMixinAppType* NewMixinAppType();
   RawPatchClass* NewPatchClass();
   RawClosureData* NewClosureData();
   RawRedirectionData* NewRedirectionData();
   RawFunction* NewFunction();
   RawField* NewField();
   RawLibrary* NewLibrary();
   RawLibraryPrefix* NewLibraryPrefix();
@@ skipping 83 matching lines @@
   friend class LibraryPrefix;
   friend class Namespace;
   friend class LiteralToken;
   friend class PatchClass;
   friend class Script;
   friend class Stacktrace;
   friend class TokenStream;
   friend class Type;
   friend class TypeArguments;
   friend class TypeParameter;
+  friend class TypeRef;
   friend class UnresolvedClass;
   friend class WeakProperty;
   friend class MirrorReference;
   DISALLOW_COPY_AND_ASSIGN(SnapshotReader);
 };
 
 
 class BaseWriter {
  public:
   // Size of the snapshot.
@@ skipping 242 matching lines @@
  private:
   SnapshotWriter* writer_;
   bool as_references_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_SNAPSHOT_H_