Do not register typechecks against type variables of typedefs.

sdk/lib/_internal/compiler/implementation/enqueue.dart

Index: sdk/lib/_internal/compiler/implementation/enqueue.dart
diff --git a/sdk/lib/_internal/compiler/implementation/enqueue.dart b/sdk/lib/_internal/compiler/implementation/enqueue.dart
index acf846242ac4f9f16e459199f907fa3f0f9d001a..10b858f1e1a1b9945583f2510c5db394e997f220 100644
--- a/sdk/lib/_internal/compiler/implementation/enqueue.dart
+++ b/sdk/lib/_internal/compiler/implementation/enqueue.dart
@@ -356,8 +356,12 @@ abstract class Enqueuer {
   }
 
   void registerIsCheck(DartType type) {
-    universe.isChecks.add(type);
-    compiler.backend.registerIsCheck(type, this);
+    // Do not register checks against type-variables of typedefs.

[ngeoffray, 2013/02/28 16:56:19]

I'd prefer if you could do that in the resolver instead. There is no "is check"
going on with a typedef.

[karlklose, 2013/02/28 17:16:45]

Done.

+    if (type.kind != TypeKind.TYPE_VARIABLE ||
+        type.element.isTypedef()) {
+      universe.isChecks.add(type);
+      compiler.backend.registerIsCheck(type, this);
+    }
   }
 
   void registerAsCheck(DartType type) {