Check cycles in redirecting factories.

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 'dart:collection' show LinkedHashMap;
 
 import 'elements.dart';
 import '../../compiler.dart' as api;
@@ skipping 1261 matching lines @@
       : super(name, kind, enclosing) {
     assert(modifiers != null);
     defaultImplementation = this;
   }
 
   bool get isPatched => patch != null;
   bool get isPatch => origin != null;
 
   bool get isRedirectingFactory => defaultImplementation != this;
 
-  FunctionElement get redirectionTarget {
-    if (this == defaultImplementation) return this;
-    var target = defaultImplementation;
-    Set<Element> seen = new Set<Element>();
-    seen.add(target);
-    while (!target.isErroneous() && target != target.defaultImplementation) {
-      target = target.defaultImplementation;
-      if (seen.contains(target)) {
-        // TODO(ahe): This is expedient for now, but it should be
-        // checked by the resolver.  Keeping http://dartbug.com/3970
-        // open to track this.
-        throw new SpannableAssertionFailure(
-            target, 'redirecting factory leads to cycle');
-      }
+  /// This field is set by the post process queue when checking for cycles.
+  FunctionElement internalRedirectionTarget;
+
+  set redirectionTarget(FunctionElement constructor) {
+    assert(constructor != null && internalRedirectionTarget == null);
+    internalRedirectionTarget = constructor;
+  }
+
+  get redirectionTarget {
+    if (Elements.isErroneousElement(defaultImplementation)) {
+      return defaultImplementation;
     }
-    return target;
+    assert(!isRedirectingFactory || internalRedirectionTarget);
+    return isRedirectingFactory ? internalRedirectionTarget
+                                : defaultImplementation;

[ngeoffray, 2013/09/18 12:52:07]

Please return null instead of defaultImplementation.

   }
 
   InterfaceType computeTargetType(Compiler compiler,
                                   InterfaceType newType) {
     if (!isRedirectingFactory) return newType;
     ClassElement targetClass = getEnclosingClass();
     TreeElements treeElements =
         compiler.enqueuer.resolution.getCachedElements(
             declaration);
     FunctionExpression functionNode = parseNode(compiler);
@@ skipping 913 matching lines @@
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   String toString() => 'MetadataAnnotation($value, $resolutionState)';
 }