[3.12] gh-119011: type.__type_params__ now return an empty tuple (GH-119296) (#119681)

(cherry picked from commit 6b240c2)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>

Author: JelleZijlstra

Lib/test/test_functools.py

@@ -705,6 +705,14 @@ def wrapper():
         self.assertTrue(wrapper.__doc__.startswith('max('))
         self.assertEqual(wrapper.__annotations__, {})
 
+    def test_update_type_wrapper(self):
+        def wrapper(*args): pass
+
+        functools.update_wrapper(wrapper, type)
+        self.assertEqual(wrapper.__name__, 'type')
+        self.assertEqual(wrapper.__annotations__, {})
+        self.assertEqual(wrapper.__type_params__, ())
+
 
 class TestWraps(TestUpdateWrapper):
 

Lib/test/test_type_params.py

@@ -499,6 +499,11 @@ class C[T]:
                                             r"Cannot use [a-z]+ in annotation scope within class scope"):
                     run_code(code.format(case))
 
+    def test_type_special_case(self):
+        # https://github.com/python/cpython/issues/119011
+        self.assertEqual(type.__type_params__, ())
+        self.assertEqual(object.__type_params__, ())
+
 
 def make_base(arg):
     class Base:

Misc/NEWS.d/next/Core and Builtins/2024-05-21-09-46-51.gh-issue-119011.WOe3bu.rst

@@ -0,0 +1,2 @@
+Fixes ``type.__type_params__`` to return an empty tuple instead of a
+descriptor.

Objects/typeobject.c

@@ -1506,8 +1506,11 @@ type_set_annotations(PyTypeObject *type, PyObject *value, void *context)
 static PyObject *
 type_get_type_params(PyTypeObject *type, void *context)
 {
-    PyObject *params = PyDict_GetItemWithError(lookup_tp_dict(type), &_Py_ID(__type_params__));
+    if (type == &PyType_Type) {
+        return PyTuple_New(0);
+    }
 
+    PyObject *params = PyDict_GetItemWithError(lookup_tp_dict(type), &_Py_ID(__type_params__));
     if (params) {
         return Py_NewRef(params);
     }