Do not register typechecks against type variables of typedefs.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

 // 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.
 
 part of resolution;
 
 abstract class TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   Selector getGetterSelectorInComplexSendSet(SendSet node);
@@ skipping 1619 matching lines @@
       // When the element is a field, we are actually resolving its
       // initial value, which should not have access to instance
       // fields.
       inInstanceContext = (element.isInstanceMember() && !element.isField())
           || element.isGenerativeConstructor(),
       this.currentClass = element.isMember() ? element.getEnclosingClass()
                                              : null,
       this.statementScope = new StatementScope(),
       typeResolver = new TypeResolver(compiler),
       scope = element.buildScope(),
-      inCheckContext = compiler.enableTypeAssertions,
+      inCheckContext = compiler.enableTypeAssertions &&
+          !element.enclosingElement.isTypedef(),

[ngeoffray, 2013/03/01 08:36:00]

Please add a comment.

       inCatchBlock = false,
       super(compiler);
 
   ResolutionEnqueuer get world => compiler.enqueuer.resolution;
 
   Element lookup(Node node, SourceString name) {
     Element result = scope.lookup(name);
     if (!Elements.isUnresolved(result)) {
       if (!inInstanceContext && result.isInstanceMember()) {
         compiler.reportErrorCode(
@@ skipping 2150 matching lines @@
     return e;
   }
 
   /// Assumed to be called by [resolveRedirectingFactory].
   Element visitReturn(Return node) {
     Node expression = node.expression;
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }