gh-104600: Make type.__type_params__ writable

Lib/test/test_builtin.py

@@ -18,6 +18,7 @@
 import sys
 import traceback
 import types
+import typing
 import unittest
 import warnings
 from contextlib import ExitStack
@@ -2485,6 +2486,17 @@ def test_type_qualname(self):
  A.__qualname__ = b'B'
  self.assertEqual(A.__qualname__, 'D.E')
 
+ def test_type_typeparams(self):
+ class A[T]:
+ pass
+ T, = A.__type_params__
+ self.assertIsInstance(T, typing.TypeVar)
+ A.__type_params__ = "whatever"
+ self.assertEqual(A.__type_params__, "whatever")
+ with self.assertRaises(TypeError):
+ del A.__type_params__
+ self.assertEqual(A.__type_params__, "whatever")
+
  def test_type_doc(self):
  for doc in 'x', '\xc4', '\U0001f40d', 'x\x00y', b'x', 42, None:
  A = type('A', (), {'__doc__': doc})

Lib/test/test_type_params.py

@@ -813,10 +813,11 @@ def test_typeparams_dunder_class_03(self):
  class ClassA[A]():
  pass
  ClassA.__type_params__ = ()
+ params = ClassA.__type_params__
  """
 
-with self.assertRaisesRegex(AttributeError, "attribute '__type_params__' of 'type' objects is not writable"):
- run_code(code)
+ns = run_code(code)
+self.assertEqual(ns["params"], ())
 
  def test_typeparams_dunder_function_01(self):
  def outer[A, B]():

Lib/test/test_typing.py

@@ -6795,6 +6795,19 @@ class Y(Generic[T], NamedTuple):
  with self.assertRaises(TypeError):
  G[int, str]
 
+ def test_generic_pep695(self):
+ class X[T](NamedTuple):
+ x: T
+ T, = X.__type_params__
+ self.assertIsInstance(T, TypeVar)
+ self.assertEqual(T.__name__, 'T')
+ self.assertEqual(X.__bases__, (tuple, Generic))
+ self.assertEqual(X.__orig_bases__, (NamedTuple, Generic[T]))
+ self.assertEqual(X.__mro__, (X, tuple, Generic, object))
+ self.assertEqual(X.__parameters__, (T,))
+ self.assertEqual(X[str].__args__, (str,))
+ self.assertEqual(X[str].__parameters__, ())
+
  def test_non_generic_subscript(self):
  # For backward compatibility, subscription works
  # on arbitrary NamedTuple types.
@@ -7205,6 +7218,20 @@ class FooBarGeneric(BarGeneric[int]):
  {'a': typing.Optional[T], 'b': int, 'c': str}
  )
 
+ def test_pep695_generic_typeddict(self):
+ class A[T](TypedDict):
+ a: T
+
+ T, = A.__type_params__
+ self.assertIsInstance(T, TypeVar)
+ self.assertEqual(T.__name__, 'T')
+ self.assertEqual(A.__bases__, (Generic, dict))
+ self.assertEqual(A.__orig_bases__, (TypedDict, Generic[T]))
+ self.assertEqual(A.__mro__, (A, Generic, dict, object))
+ self.assertEqual(A.__parameters__, (T,))
+ self.assertEqual(A[str].__parameters__, ())
+ self.assertEqual(A[str].__args__, (str,))
+
  def test_generic_inheritance(self):
  class A(TypedDict, Generic[T]):
  a: T

Objects/typeobject.c

@@ -1460,18 +1460,6 @@ type_get_annotations(PyTypeObject *type, void *context)
  return annotations;
 }
 
-static PyObject *
-type_get_type_params(PyTypeObject *type, void *context)
-{
- PyObject *params = PyDict_GetItem(lookup_tp_dict(type), &_Py_ID(__type_params__));
-
- if (params) {
- return Py_NewRef(params);
- }
-
- return PyTuple_New(0);
-}
-
 static int
 type_set_annotations(PyTypeObject *type, PyObject *value, void *context)
 {
@@ -1502,6 +1490,34 @@ type_set_annotations(PyTypeObject *type, PyObject *value, void *context)
  return result;
 }
 
+static PyObject *
+type_get_type_params(PyTypeObject *type, void *context)
+{
+ PyObject *params = PyDict_GetItem(lookup_tp_dict(type), &_Py_ID(__type_params__));
+
+ if (params) {
+ return Py_NewRef(params);
+ }
+
+ return PyTuple_New(0);
+}
+
+static int
+type_set_type_params(PyTypeObject *type, PyObject *value, void *context)
+{
+ if (!check_set_special_type_attr(type, value, "__type_params__")) {
+ return -1;
+ }
+
+ PyObject *dict = lookup_tp_dict(type);
+ int result = PyDict_SetItem(dict, &_Py_ID(__type_params__), value);
+
+ if (result == 0) {
+ PyType_Modified(type);
+ }
+ return result;
+}
+
 
 /*[clinic input]
 type.__instancecheck__ -> bool
@@ -1548,7 +1564,7 @@ static PyGetSetDef type_getsets[] = {
  {"__doc__", (getter)type_get_doc, (setter)type_set_doc, NULL},
  {"__text_signature__", (getter)type_get_text_signature, NULL, NULL},
  {"__annotations__", (getter)type_get_annotations, (setter)type_set_annotations, NULL},
- {"__type_params__", (getter)type_get_type_params, NULL, NULL},
+ {"__type_params__", (getter)type_get_type_params, (setter)type_set_type_params, NULL},
  {0}
 };