From f1a757607a5a53eaa79fe42da7da398d65296fff Mon Sep 17 00:00:00 2001
From: CF Bolz-Tereick <cfbolz@gmx.de>
Date: Fri, 27 Dec 2024 02:03:47 +0100
Subject: [PATCH] gh-127537: Add __class_getitem__ to the python implementation
 of functools.partial (#127537)

(cherry picked from commit 401bba6b58497ce59e7b45ad33e43ae8c67abcb9)
---
 Lib/functools.py                                           | 3 +++
 Lib/test/test_functools.py                                 | 7 +++++++
 .../Library/2024-12-04-10-39-29.gh-issue-83662.CG1s3m.rst  | 5 +++++
 3 files changed, 15 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2024-12-04-10-39-29.gh-issue-83662.CG1s3m.rst

diff --git a/Lib/functools.py b/Lib/functools.py
index f6849899e7578e..6025032bfaa233 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -340,6 +340,9 @@ def __setstate__(self, state):
         self.args = args
         self.keywords = kwds
 
+    __class_getitem__ = classmethod(GenericAlias)
+
+
 try:
     from _functools import partial
 except ImportError:
diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index ff71fd53c08a69..dadcd04394b390 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -390,6 +390,13 @@ def __getitem__(self, key):
         f = self.partial(object)
         self.assertRaises(TypeError, f.__setstate__, BadSequence())
 
+    def test_partial_genericalias(self):
+        alias = self.partial[int]
+        self.assertIs(alias.__origin__, self.partial)
+        self.assertEqual(alias.__args__, (int,))
+        self.assertEqual(alias.__parameters__, ())
+
+
 @unittest.skipUnless(c_functools, 'requires the C _functools module')
 class TestPartialC(TestPartial, unittest.TestCase):
     if c_functools:
diff --git a/Misc/NEWS.d/next/Library/2024-12-04-10-39-29.gh-issue-83662.CG1s3m.rst b/Misc/NEWS.d/next/Library/2024-12-04-10-39-29.gh-issue-83662.CG1s3m.rst
new file mode 100644
index 00000000000000..5e39933047993c
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-12-04-10-39-29.gh-issue-83662.CG1s3m.rst
@@ -0,0 +1,5 @@
+Add missing ``__class_getitem__`` method to the Python implementation of
+:func:`functools.partial`, to make it compatible with the C version. This is
+mainly relevant for alternative Python implementations like PyPy and
+GraalPy, because CPython will usually use the C-implementation of that
+function.