Fix #82: Avoid creating a side-effect in typing module. (#337)

Co-authored-by: Olivier Grisel <olivier.grisel@ensta.org>

CHANGES.md

@@ -4,9 +4,6 @@
 - Fix a bug affecting dynamic modules occuring with modified builtins
   ([issue #316](https://github.com/cloudpipe/cloudpickle/issues/316))
 
-1.2.3
-=====
-
 - Fix a bug affecting cloudpickle when non-modules objects are added into
   sys.modules
   ([PR #326](https://github.com/cloudpipe/cloudpickle/pull/326)).
@@ -23,6 +20,10 @@
   https://docs.python.org/3/library/pickle.html#example
   ([issue #308](https://github.com/cloudpipe/cloudpickle/pull/308))
 
+- Fix a side effect that would redefine `types.ClassTypes` as `type`
+  when importing cloudpickle.
+  ([issue #337](https://github.com/cloudpipe/cloudpickle/pull/337))
+
 1.2.2
 =====
 

cloudpickle/__init__.py

@@ -8,4 +8,4 @@
 if sys.version_info[:2] >= (3, 8):
     from cloudpickle.cloudpickle_fast import CloudPickler, dumps, dump
 
-__version__ = '1.2.3dev0'
+__version__ = '1.3.0dev0'

cloudpickle/cloudpickle.py

@@ -95,7 +95,6 @@
     PY3 = False
     PY2 = True
 else:
-    types.ClassType = type
     from pickle import _Pickler as Pickler
     from io import BytesIO as StringIO
     string_types = (str,)
@@ -889,7 +888,8 @@ def save_global(self, obj, name=None, pack=struct.pack):
             Pickler.save_global(self, obj, name=name)
 
     dispatch[type] = save_global
-    dispatch[types.ClassType] = save_global
+    if PY2:
+        dispatch[types.ClassType] = save_global
 
     def save_instancemethod(self, obj):
         # Memoization rarely is ever useful due to python bounding