Implement is-checks against type variables.

sdk/lib/_internal/compiler/implementation/enqueue.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 dart2js;
 
 class EnqueueTask extends CompilerTask {
   final ResolutionEnqueuer resolution;
   final CodegenEnqueuer codegen;
 
@@ skipping 68 matching lines @@
 
   /**
    * Adds [element] to the work list if it has not already been processed.
    *
    * Returns [:true:] if the [element] should be processed.
    */
   // TODO(johnniwinther): Change to 'Returns true if the element was added to
   // the work list'?
   bool addElementToWorkList(Element element, [TreeElements elements]);
 
+  void registerInstantiatedType(InterfaceType type) {
+    universe.instantiatedTypes.add(type);
+    registerInstantiatedClass(type.element);
+  }
+
   void registerInstantiatedClass(ClassElement cls) {
     if (universe.instantiatedClasses.contains(cls)) return;
     if (!cls.isAbstract(compiler)) {
       universe.instantiatedClasses.add(cls);
     }
     onRegisterInstantiatedClass(cls);
     compiler.backend.registerInstantiatedClass(cls, this);
   }
 
   bool checkNoEnqueuedInvokedInstanceMethods() {
@@ skipping 427 matching lines @@
     while(!queue.isEmpty) {
       // TODO(johnniwinther): Find an optimal process order for codegen.
       f(queue.removeLast());
     }
   }
 
   void _logSpecificSummary(log(message)) {
     log('Compiled ${generatedCode.length} methods.');
   }
 }