Make hasNext a getter instead of a method.

lib/core/sequences.dart

Index: lib/core/sequences.dart
diff --git a/lib/core/sequences.dart b/lib/core/sequences.dart
index 5ed4366aa2e91f58330897c94e713d0d814d0c27..c200d1bf355a5d80074f1ac0a97798f246d56de8 100644
--- a/lib/core/sequences.dart
+++ b/lib/core/sequences.dart
@@ -195,9 +195,9 @@ class SequenceIterator<E> implements Iterator<E> {
   Sequence<E> _sequence;
   int _position;
   SequenceIterator(this._sequence) : _position = 0;
-  bool hasNext() => _position < _sequence.length;
+  bool get hasNext => _position < _sequence.length;
   E next() {
-    if (hasNext()) return _sequence[_position++];
+    if (hasNext) return _sequence[_position++];
     throw new NoMoreElementsException();
   }
 }