diff --git a/Lib/test/test_type_aliases.py b/Lib/test/test_type_aliases.py index f8b395fdc8bb1d..4c17933e7f7c23 100644 --- a/Lib/test/test_type_aliases.py +++ b/Lib/test/test_type_aliases.py @@ -212,6 +212,19 @@ def test_generic(self): self.assertEqual(TA.__value__, list[T]) self.assertEqual(TA.__type_params__, (T,)) self.assertEqual(TA.__module__, __name__) + self.assertIs(type(TA[int]), types.GenericAlias) + + def test_not_generic(self): + TA = TypeAliasType("TA", list[int], type_params=()) + self.assertEqual(TA.__name__, "TA") + self.assertEqual(TA.__value__, list[int]) + self.assertEqual(TA.__type_params__, ()) + self.assertEqual(TA.__module__, __name__) + with self.assertRaisesRegex( + TypeError, + "Only generic type aliases are subscriptable", + ): + TA[int] def test_keywords(self): TA = TypeAliasType(name="TA", value=int) diff --git a/Misc/NEWS.d/next/Library/2024-09-25-12-14-58.gh-issue-124498.Ozxs55.rst b/Misc/NEWS.d/next/Library/2024-09-25-12-14-58.gh-issue-124498.Ozxs55.rst new file mode 100644 index 00000000000000..4dbf4eb709733d --- /dev/null +++ b/Misc/NEWS.d/next/Library/2024-09-25-12-14-58.gh-issue-124498.Ozxs55.rst @@ -0,0 +1,2 @@ +Fix :class:`typing.TypeAliasType` not to be generic, when ``type_params`` is +an empty tuple. diff --git a/Objects/typevarobject.c b/Objects/typevarobject.c index c8ab14053de418..f3e3ed0c9afae7 100644 --- a/Objects/typevarobject.c +++ b/Objects/typevarobject.c @@ -1640,7 +1640,16 @@ typealias_alloc(PyObject *name, PyObject *type_params, PyObject *compute_value, return NULL; } ta->name = Py_NewRef(name); - ta->type_params = Py_IsNone(type_params) ? NULL : Py_XNewRef(type_params); + if ( + type_params == NULL + || Py_IsNone(type_params) + || (PyTuple_Check(type_params) && PyTuple_GET_SIZE(type_params) == 0) + ) { + ta->type_params = NULL; + } + else { + ta->type_params = Py_NewRef(type_params); + } ta->compute_value = Py_XNewRef(compute_value); ta->value = Py_XNewRef(value); ta->module = Py_XNewRef(module);