fix(Key): made key equality asymmetrical

lib/key.dart

@@ -12,7 +12,7 @@ class Key {
   final int id;
 
   factory Key(Type type, [Type annotation]) {
-    var _hashCode = type.hashCode + annotation.hashCode;
+    var _hashCode = type.hashCode + 2339 * annotation.hashCode;
     var _id = _hashToKey.putIfAbsent(_hashCode, () => _lastKeyId++);
     return new Key._newKey(type, annotation, _hashCode, _id);
   }

test/fixed-unittest.dart

@@ -25,26 +25,7 @@ Matcher toThrow(Type exceptionClass, [message]) => message == null
           instanceOf(exceptionClass),
           message is Matcher ? message : toContain(message)));
 
-Matcher not(Matcher matcher) => new NegateMatcher(matcher);
-
-
-class NegateMatcher extends Matcher {
-  final Matcher _matcher;
-
-  const NegateMatcher(this._matcher);
-
-  bool matches(obj, Map ms) => !_matcher.matches(obj, ms);
-
-  Description describe(Description description) =>
-      _matcher.describe(description.add('NOT'));
-
-  Description describeMismatch(item, Description mismatchDescription,
-      Map matchState, bool verbose) {
-    return _matcher.describeMismatch(
-        item, mismatchDescription, matchState, verbose);
-  }
-}
-
+Matcher not(Matcher matcher) => isNot(matcher);
 
 class ThrowsMatcher extends Throws {
   final Matcher _matcher;

test/main.dart

@@ -856,5 +856,12 @@ createKeySpec() {
       expect(k1, not(equals(k2)));
       expect(k1.hashCode, not(equals(k2.hashCode)));
     });
+
+    it('should not be symmetrically equal', () {
+      Key k1 = new Key(Engine, Old);
+      Key k2 = new Key(Old, Engine);
+      expect(k1, not(equals(k2)));
+      expect(k1.hashCode, not(equals(k2.hashCode)));
+    });
   });
 }