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gh-150146: Fix NULL dereference in _Py_subs_parameters #150147

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gh-150146: Fix NULL dereference in _Py_subs_parameters #150147

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13 changes: 10 additions & 3 deletions Lib/test/test_genericalias.py
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Original file line number Diff line number Diff line change
Expand Up @@ -55,15 +55,14 @@
from unittest.case import _AssertRaisesContext
from queue import Queue, SimpleQueue
from weakref import WeakSet, ReferenceType, ref
import typing
from typing import Unpack
try:
from tkinter import Event
except ImportError:
Event = None
from string.templatelib import Template, Interpolation

from typing import TypeVar
import typing
from typing import TypeVar, Unpack
T = TypeVar('T')
K = TypeVar('K')
V = TypeVar('V')
Expand Down Expand Up @@ -621,6 +620,14 @@ def test_nested_paramspec_specialization(self):
self.assertEqual(deeply_nested_specialized.__args__, ([str, [float], int], float))
self.assertEqual(deeply_nested_specialized.__parameters__, ())

def test_gh150146(self):
# It used to crash:
for container in [memoryview, list, tuple]:
with self.subTest(container=container):
x = container[TypeVar("")]
with self.assertRaises(TypeError):
x[*typing.Mapping[..., ...]]


class TypeIterationTests(unittest.TestCase):
_UNITERABLE_TYPES = (list, tuple)
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5 changes: 5 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-05-20-13-06-17.gh-issue-150146.i5m_SL.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
Fix a crash on a complex type variable substitution.

``from typing import TypeVar; memoryview[TypeVar("")][*typing.Mapping[...,
...]]`` used to fail due to missing ``NULL`` check on ``_unpack_args`` C
function call.
3 changes: 3 additions & 0 deletions Objects/genericaliasobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -412,6 +412,9 @@ _Py_subs_parameters(PyObject *self, PyObject *args, PyObject *parameters, PyObje
self);
}
item = _unpack_args(item);
if (item == NULL) {
return NULL;
}
for (Py_ssize_t i = 0; i < nparams; i++) {
PyObject *param = PyTuple_GET_ITEM(parameters, i);
PyObject *prepare, *tmp;
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