Make MapMutation unpickleable

2 files changed, 6 insertions, 0 deletions

diff --git a/immutables/map.py b/immutables/map.py
index 73581ed..fc40ac8 100644
--- a/immutables/map.py
+++ b/immutables/map.py
@@ -722,6 +722,9 @@ class MapMutation:
     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__))
 
diff --git a/tests/test_map.py b/tests/test_map.py
index d7ee885..959e00c 100644
--- a/tests/test_map.py
+++ b/tests/test_map.py
@@ -1254,6 +1254,9 @@ class BaseMapTest:
             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):