Make isEmpty a getter.

lib/coreimpl/hash_map_set.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.
 
 // Hash map implementation with open addressing and quadratic probing.
 class HashMapImplementation<K, V> implements HashMap<K, V> {
 
   // The [_keys] list contains the keys inserted in the map.
   // The [_keys] list must be a raw list because it
   // will contain both elements of type K, and the [_DELETED_KEY] of type
@@ skipping 201 matching lines @@
       V value = _values[index];
       _values[index] = null;
       // Set the key to the sentinel to not break the probing chain.
       _keys[index] = _DELETED_KEY;
       _numberOfDeleted++;
       return value;
     }
     return null;
   }
 
-  bool isEmpty() {
+  bool get isEmpty {
     return _numberOfEntries == 0;
   }
 
   int get length {
     return _numberOfEntries;
   }
 
   void forEach(void f(K key, V value)) {
     int length = _keys.length;
     for (int i = 0; i < length; i++) {
@@ skipping 135 matching lines @@
   bool every(bool f(E element)) {
     Collection<E> keys = _backingMap.getKeys();
     return keys.every(f);
   }
 
   bool some(bool f(E element)) {
     Collection<E> keys = _backingMap.getKeys();
     return keys.some(f);
   }
 
-  bool isEmpty() {
-    return _backingMap.isEmpty();
+  bool get isEmpty {
+    return _backingMap.isEmpty;
   }
 
   int get length {
     return _backingMap.length;
   }
 
   Iterator<E> iterator() {
     return new HashSetIterator<E>(this);
   }
 
@@ skipping 57 matching lines @@
 
 /**
  * A singleton sentinel used to represent when a key is deleted from the map.
  * We can't use [: const Object() :] as a sentinel because it would end up
  * canonicalized and then we cannot distinguish the deleted key from the
  * canonicalized [: Object() :].
  */
 class _DeletedKeySentinel {
   const _DeletedKeySentinel();
 }