[3.15] gh-157621: Clear weakrefs for ParamSpec attributes (GH-157622) (#157653)

gh-157621: Clear weakrefs for ParamSpec attributes (GH-157622)
(cherry picked from commit b215552)

Co-authored-by: Samartha <samarthat9@gmail.com>

Author: miss-islington

Lib/test/test_typing.py

@@ -10285,6 +10285,17 @@ def test_args_kwargs(self):
         self.assertEqual(repr(P.args), "P.args")
         self.assertEqual(repr(P.kwargs), "P.kwargs")
 
+    def test_args_kwargs_weakrefs(self):
+        P = ParamSpec('P')
+        for attr_name in ('args', 'kwargs'):
+            with self.subTest(attr_name=attr_name):
+                callback_fired = []
+                attr = getattr(P, attr_name)
+                ref = weakref.ref(attr, lambda _: callback_fired.append(True))
+                del attr
+                self.assertEqual(callback_fired, [True])
+                self.assertIsNone(ref())
+
     def test_stringized(self):
         P = ParamSpec('P')
         class C(Generic[P]):

Misc/NEWS.d/next/Library/2026-09-16-14-04-38.gh-issue-157621.R6v2S8.rst

@@ -0,0 +1,2 @@
+Fix a crash when a weak-reference callback is attached to a
+:class:`typing.ParamSpecArgs` or :class:`typing.ParamSpecKwargs` instance.

Objects/typevarobject.c

@@ -958,6 +958,7 @@ paramspecattr_dealloc(PyObject *self)
     _PyObject_GC_UNTRACK(self);
 
     Py_XDECREF(psa->__origin__);
+    PyObject_ClearWeakRefs(self);
 
     Py_TYPE(self)->tp_free(self);
     Py_DECREF(tp);