fix generic const canonicalization bug

frog/leg/scanner/listener.dart

 // Copyright (c) 2011, 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.
 
 final bool VERBOSE = false;
 
 class Listener {
   void beginArguments(Token token) {
   }
 
@@ skipping 532 matching lines @@
   void handleUnaryPostfixExpression(Token token) {
     pushNode(new Send.postfix(popNode(), new Operator(token)));
   }
 
   void handleUnaryPrefixExpression(Token token) {
     pushNode(new Send.prefix(popNode(), new Operator(token)));
   }
 
   NodeList makeNodeList(int count, Token beginToken, Token endToken,
                         String delimiter) {
-    // TODO(ahe): Remove below comment about Frog bug when it is fixed.
-    Link<Node> nodes = const EmptyLink<Node>(); // Type warning is Frog bug.
+    Link<Node> nodes = const EmptyLink<Node>();
     for (; count > 0; --count) {
       // This effectively reverses the order of nodes so they end up
       // in correct (source) order.
       nodes = nodes.prepend(popNode());
     }
     SourceString sourceDelimiter =
         (delimiter === null) ? null : new SourceString(delimiter);
     return new NodeList(beginToken, nodes, endToken, sourceDelimiter);
   }
 
@@ skipping 33 matching lines @@
     return node;
   }
 }
 
 Node parse(Canceler canceler, Logger logger, doParse(Parser parser)) {
   NodeListener listener = new NodeListener(canceler, logger);
   doParse(new Parser(listener));
   Node node = listener.popNode();
   return node;
 }