[Python-checkins] gh-94607: Fix subclassing generics (GH-94610)
miss-islington
webhook-mailer at python.org
Sat Jul 9 01:20:55 EDT 2022
https://github.com/python/cpython/commit/b4e232c4b5d977578b3c6aa86d8b76085167c313
commit: b4e232c4b5d977578b3c6aa86d8b76085167c313
branch: 3.11
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: miss-islington <31488909+miss-islington at users.noreply.github.com>
date: 2022-07-08T22:20:43-07:00
summary:
gh-94607: Fix subclassing generics (GH-94610)
Co-authored-by: Serhiy Storchaka <3659035+serhiy-storchaka at users.noreply.github.com>
(cherry picked from commit 6442a9dd212fa18343db21849cf05c0181662c1f)
Co-authored-by: Ken Jin <28750310+Fidget-Spinner at users.noreply.github.com>
files:
A Misc/NEWS.d/next/Library/2022-07-06-16-01-08.gh-issue-94607.Q6RYfz.rst
M Lib/test/test_typing.py
M Lib/typing.py
M Objects/genericaliasobject.c
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 634be9062d633..2fd57822726e5 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -3644,6 +3644,35 @@ def test_subclass_special_form(self):
class Foo(obj):
pass
+ def test_complex_subclasses(self):
+ T_co = TypeVar("T_co", covariant=True)
+
+ class Base(Generic[T_co]):
+ ...
+
+ T = TypeVar("T")
+
+ # see gh-94607: this fails in that bug
+ class Sub(Base, Generic[T]):
+ ...
+
+ def test_parameter_detection(self):
+ self.assertEqual(List[T].__parameters__, (T,))
+ self.assertEqual(List[List[T]].__parameters__, (T,))
+ class A:
+ __parameters__ = (T,)
+ # Bare classes should be skipped
+ for a in (List, list):
+ for b in (A, int, TypeVar, TypeVarTuple, ParamSpec, types.GenericAlias, types.UnionType):
+ with self.subTest(generic=a, sub=b):
+ with self.assertRaisesRegex(TypeError, '.* is not a generic class'):
+ a[b][str]
+ # Duck-typing anything that looks like it has __parameters__.
+ # These tests are optional and failure is okay.
+ self.assertEqual(List[A()].__parameters__, (T,))
+ # C version of GenericAlias
+ self.assertEqual(list[A()].__parameters__, (T,))
+
class ClassVarTests(BaseTestCase):
def test_basics(self):
diff --git a/Lib/typing.py b/Lib/typing.py
index 1ebc3ce1f64bd..31269273a5c0d 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -250,6 +250,9 @@ def _collect_parameters(args):
"""
parameters = []
for t in args:
+ # We don't want __parameters__ descriptor of a bare Python class.
+ if isinstance(t, type):
+ continue
if hasattr(t, '__typing_subst__'):
if t not in parameters:
parameters.append(t)
diff --git a/Misc/NEWS.d/next/Library/2022-07-06-16-01-08.gh-issue-94607.Q6RYfz.rst b/Misc/NEWS.d/next/Library/2022-07-06-16-01-08.gh-issue-94607.Q6RYfz.rst
new file mode 100644
index 0000000000000..3bbb9172f2619
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-07-06-16-01-08.gh-issue-94607.Q6RYfz.rst
@@ -0,0 +1,2 @@
+Fix subclassing complex generics with type variables in :mod:`typing`. Previously an error message saying ``Some type variables ... are not listed in Generic[...]`` was shown.
+:mod:`typing` no longer populates ``__parameters__`` with the ``__parameters__`` of a Python class.
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index b2636d5475dbb..19f011fd3a743 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -219,6 +219,10 @@ _Py_make_parameters(PyObject *args)
for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
PyObject *t = PyTuple_GET_ITEM(args, iarg);
PyObject *subst;
+ // We don't want __parameters__ descriptor of a bare Python class.
+ if (PyType_Check(t)) {
+ continue;
+ }
if (_PyObject_LookupAttr(t, &_Py_ID(__typing_subst__), &subst) < 0) {
Py_DECREF(parameters);
return NULL;
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