Make MapMutation unpickleable

Author: 1st1

immutables/map.py

@@ -722,6 +722,9 @@ def __repr__(self):
     def __len__(self):
         return self.__count
 
+    def __reduce__(self):
+        raise TypeError("can't pickle {} objects".format(type(self).__name__))
+
     def __hash__(self):
         raise TypeError('unhashable type: {}'.format(type(self).__name__))
 

tests/test_map.py

@@ -1254,6 +1254,9 @@ def test_map_pickle(self):
             self.assertTrue(isinstance(uh, self.Map))
             self.assertEqual(h, uh)
 
+        with self.assertRaisesRegex(TypeError, "can't pickle"):
+            pickle.dumps(h.mutate())
+
 
 class PyMapTest(BaseMapTest, unittest.TestCase):