Do not register typechecks against type variables of typedefs.

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

Index: sdk/lib/_internal/compiler/implementation/resolution/members.dart
diff --git a/sdk/lib/_internal/compiler/implementation/resolution/members.dart b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
index 03509e799d557d2d30e3bf41d45c3198dda401b1..b19582be75a90cf9e023e1fe24eaae032fbe82bb 100644
--- a/sdk/lib/_internal/compiler/implementation/resolution/members.dart
+++ b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
@@ -1747,7 +1747,9 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
     DartType type = resolveTypeAnnotation(node);
     if (type != null) {
       if (inCheckContext) {
-        compiler.enqueuer.resolution.registerIsCheck(type);
+        if (!Types.isTypeVariableOfTypedef(type)) {
+          compiler.enqueuer.resolution.registerIsCheck(type);
+	}
       }
       return type.element;
     }
@@ -2568,7 +2570,9 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
         onFailure: report, whenResolved: useType);
     if (type == null) return null;
     if (inCheckContext) {
-      compiler.enqueuer.resolution.registerIsCheck(type);
+      if (!Types.isTypeVariableOfTypedef(type)) {
+        compiler.enqueuer.resolution.registerIsCheck(type);
+      }
     }
     if (typeRequired || inCheckContext) {
       if (type is InterfaceType) {