Make hasNext a getter instead of a method.

lib/coreimpl/collections.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.
 
 /**
  * The [Collections] class implements static methods useful when
  * writing a class that implements [Collection] and the [iterator]
  * method.
  */
 class Collections {
@@ skipping 41 matching lines @@
   }
 
   static List filter(Iterable source, List destination, bool f(o)) {
     for (final e in source) {
       if (f(e)) destination.add(e);
     }
     return destination;
   }
 
   static bool isEmpty(Iterable iterable) {
-    return !iterable.iterator().hasNext();
+    return !iterable.iterator().hasNext;
   }
 
   // TODO(jjb): visiting list should be an identityHashSet when it exists
 
   /**
    * Returns a string representing the specified collection. If the
    * collection is a [List], the returned string looks like this:
    * [:'[element0, element1, ... elementN]':]. The value returned by its
    * [toString] method is used to represent each element. If the specified
    * collection is not a list, the returned string looks like this:
@@ skipping 80 matching lines @@
    * Returns true if the specified collection contains the specified object
    * reference.
    */
   static _containsRef(Collection c, Object ref) {
     for (var e in c) {
       if (e === ref) return true;
     }
     return false;
   }
 }