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

runtime/vm/ast.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_AST_H_
 #define VM_AST_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/growable_array.h"
@@ skipping 352 matching lines @@
 };
 
 
 class TypeNode : public AstNode {
  public:
   TypeNode(intptr_t token_pos, const AbstractType& type)
       : AstNode(token_pos), type_(type) {
     ASSERT(type_.IsZoneHandle());
     ASSERT(!type_.IsNull());
     ASSERT(type_.IsFinalized());
+    // A wellformed literal Type must be canonical.
+    ASSERT(!type_.IsType() ||
+           type_.IsMalformedOrMalbounded() ||
+           type_.IsCanonical());
   }
 
   const AbstractType& type() const { return type_; }
 
   const char* TypeName() const;
 
   virtual const Instance* EvalConstExpr() const {
     if (!type_.IsInstantiated() || type_.IsMalformedOrMalbounded()) {
       return NULL;
     }
@@ skipping 1386 matching lines @@
   const intptr_t try_index_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(InlinedFinallyNode);
 };
 
 }  // namespace dart
 
 #undef DECLARE_COMMON_NODE_FUNCTIONS
 
 #endif  // VM_AST_H_