Make hashCode a getter and not a method.

tests/language/arithmetic_test.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.
 // Dart test program to test arithmetic operations.
 
 #library('arithmetic_test');
 #import('dart:math');
 
 class ArithmeticTest {
 
@@ skipping 388 matching lines @@
 
     // Min/max
     Expect.equals(1, min(1, 12));
     Expect.equals(12, max(1, 12));
     Expect.equals(1.0, min(1.0, 12.0));
     Expect.equals(12.0, max(1.0, 12.0));
     Expect.equals(false, 1.0 < min(1.0, 12.0));
     Expect.equals(true, 1.0 < max(1.0, 12.0));
 
     // Hashcode
-    Expect.equals(false, (3.4).hashCode() == (1.2).hashCode());
-    Expect.equals(true, (1.2).hashCode() == (1.2).hashCode());
-    Expect.equals(false, (3).hashCode() == (1).hashCode());
-    Expect.equals(true, (10).hashCode() == (10).hashCode());
+    Expect.equals(false, (3.4).hashCode == (1.2).hashCode);
+    Expect.equals(true, (1.2).hashCode == (1.2).hashCode);
+    Expect.equals(false, (3).hashCode == (1).hashCode);
+    Expect.equals(true, (10).hashCode == (10).hashCode);
   }
 
   static testMain() {
     for (int i = 0; i < 1500; i++) {
       runOne();
     }
   }
 }
 
 main() {
   ArithmeticTest.testMain();
 }