Add pickling tests, fix refcounting bug

Author: JelleZijlstra

Lib/test/test_type_aliases.py

@@ -1,3 +1,4 @@
+import pickle
 import types
 import unittest
 from test.support import check_syntax_error, run_code
@@ -214,3 +215,9 @@ def test_module(self):
                          mod_generics_cache.__name__)
         self.assertEqual(mod_generics_cache.OldStyle.__module__,
                          mod_generics_cache.__name__)
+
+    def test_pickling(self):
+        pickled = pickle.dumps(mod_generics_cache.Alias)
+        self.assertIs(pickle.loads(pickled), mod_generics_cache.Alias)
+        pickled = pickle.dumps(mod_generics_cache.OldStyle)
+        self.assertIs(pickle.loads(pickled), mod_generics_cache.OldStyle)

Objects/typevarobject.c

@@ -1319,7 +1319,8 @@ typealias_module(PyObject *self, void *unused)
         return Py_NewRef(ta->module);
     }
     if (ta->compute_value != NULL) {
-        return PyFunction_GetModule(ta->compute_value);
+        // PyFunction_GetModule() returns a borrowed reference
+        return Py_NewRef(PyFunction_GetModule(ta->compute_value));
     }
     Py_RETURN_NONE;
 }