Issue #22653: Fix an assertion failure in debug mode when doing a reentrant dict insertion in debug mode.

Lib/test/test_dict.py

@@ -906,6 +906,35 @@ class DictTest(unittest.TestCase):
         f.a = 'a'
         self.assertEqual(f.__dict__, {1:1, 'a':'a'})
 
+    def check_reentrant_insertion(self, mutate):
+        # This object will trigger mutation of the dict when replaced
+        # by another value.  Note this relies on refcounting: the test
+        # won't achieve its purpose on fully-GCed Python implementations.
+        class Mutating:
+            def __del__(self):
+                mutate(d)
+
+        d = {k: Mutating() for k in 'abcdefghijklmnopqr'}
+        for k in list(d):
+            d[k] = k
+
+    def test_reentrant_insertion(self):
+        # Reentrant insertion shouldn't crash (see issue #22653)
+        def mutate(d):
+            d['b'] = 5
+        self.check_reentrant_insertion(mutate)
+
+        def mutate(d):
+            d.update(self.__dict__)
+            d.clear()
+        self.check_reentrant_insertion(mutate)
+
+        def mutate(d):
+            while d:
+                d.popitem()
+        self.check_reentrant_insertion(mutate)
+
+
 from test import mapping_tests
 
 class GeneralMappingTests(mapping_tests.BasicTestMappingProtocol):