dart2js cps: 'is' checks on types with type arguments.

pkg/compiler/lib/src/tree_ir/optimization/pull_into_initializers.dart

 // Copyright (c) 2015, 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.
 
 import 'optimization.dart' show Pass;
 import '../tree_ir_nodes.dart';
 
 /// Pulls assignment expressions to the top of the function body so they can be
 /// translated into declaration-site variable initializaters.
 ///
@@ skipping 229 matching lines @@
       entry.key = visitExpression(entry.key);
       if (seenImpure) return node;
       entry.value = visitExpression(entry.value);
       if (seenImpure) return node;
     }
     if (node.type != null) seenImpure = true; // Type casts can throw.
     return node;
   }
 
   Expression visitTypeOperator(TypeOperator node) {
-    node.receiver = visitExpression(node.receiver);
+    node.value = visitExpression(node.value);
+    if (seenImpure) return node;
+    rewriteList(node.typeArguments);
     if (!node.isTypeTest) seenImpure = true; // Type cast can throw.
     return node;
   }
 
   void visitInnerFunction(FunctionDefinition node) {
     node.body = new BodyRewriter().rewriteBody(node.parameters, node.body);
   }
 
   Expression visitFunctionExpression(FunctionExpression node) {
     visitInnerFunction(node.definition);
@@ skipping 63 matching lines @@
 
   Expression visitVariableUse(VariableUse node) {
     return node;
   }
 
   Expression visitCreateInvocationMirror(CreateInvocationMirror node) {
     rewriteList(node.arguments);
     return node;
   }
 }