Update check for cyclic typedefs.

sdk/lib/_internal/compiler/implementation/elements/modelx.dart

 // Copyright (c) 2013, 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.
 
 library elements.modelx;
 
 import 'elements.dart';
 import '../../compiler.dart' as api;
 import '../tree/tree.dart';
 import '../util/util.dart';
@@ skipping 977 matching lines @@
    *
    * The [rawType] is computed together with [thisType] in [computeType].
    */
   TypedefType rawType;
 
   /**
    * The type annotation which defines this typedef.
    */
   DartType alias;
 
+  /// [:true:] if the typedef has been checked for cyclic reference.
+  bool hasBeenCheckedForCycles = false;
+
   bool get isResolved => mapping != null;
 
   // TODO(johnniwinther): Store the mapping in the resolution enqueuer instead.
   TreeElements mapping;
 
   TypedefElementX(SourceString name, Element enclosing)
       : super(name, ElementKind.TYPEDEF, enclosing);
 
   /**
    * Function signature for a typedef of a function type. The signature is
@@ skipping 23 matching lines @@
     }
     compiler.resolveTypedef(this);
     return thisType;
   }
 
   Link<DartType> get typeVariables => thisType.typeArguments;
 
   Scope buildScope() {
     return new TypeDeclarationScope(enclosingElement.buildScope(), this);
   }
+
+  void checkCyclicReference(Compiler compiler) {
+    if (hasBeenCheckedForCycles) return;
+    var visitor = new TypedefCyclicVisitor(compiler, this);
+    computeType(compiler).accept(visitor, null);
+    hasBeenCheckedForCycles = true;
+  }
 }
 
 class VariableElementX extends ElementX implements VariableElement {
   final VariableListElement variables;
   Expression cachedNode; // The send or the identifier in the variables list.
 
   Modifiers get modifiers => variables.modifiers;
 
   VariableElementX(SourceString name,
                    VariableListElement variables,
@@ skipping 1276 matching lines @@
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   String toString() => 'MetadataAnnotation($value, $resolutionState)';
 }