Fixed #31223 -- Added __class_getitem__() to Manager and QuerySet.

django/db/models/manager.py

@@ -35,6 +35,9 @@ class BaseManager:
         """Return "app_label.model_label.manager_name"."""
         return '%s.%s' % (self.model._meta.label, self.name)
 
+    def __class_getitem__(cls, *args, **kwargs):
+        return cls
+
     def deconstruct(self):
         """
         Return a 5-tuple of the form (as_manager (True), manager_class,

django/db/models/query.py

@@ -323,6 +323,9 @@ class QuerySet:
         qs._fetch_all()
         return qs._result_cache[0]
 
+    def __class_getitem__(cls, *args, **kwargs):
+        return cls
+
     def __and__(self, other):
         self._merge_sanity_check(other)
         if isinstance(other, EmptyQuerySet):

tests/managers_regress/tests.py

@@ -1,7 +1,10 @@
+from unittest import skipUnless
+
 from django.db import models
 from django.template import Context, Template
 from django.test import SimpleTestCase, TestCase, override_settings
 from django.test.utils import isolate_apps
+from django.utils.version import PY37
 
 from .models import (
     AbstractBase1, AbstractBase2, AbstractBase3, Child1, Child2, Child3,
@@ -285,3 +288,7 @@ class TestManagerInheritance(SimpleTestCase):
 
         self.assertEqual(TestModel._meta.managers, (TestModel.custom_manager,))
         self.assertEqual(TestModel._meta.managers_map, {'custom_manager': TestModel.custom_manager})
+
+    @skipUnless(PY37, '__class_getitem__() was added in Python 3.7')
+    def test_manager_class_getitem(self):
+        self.assertIs(models.Manager[Child1], models.Manager)

tests/model_inheritance/tests.py

@@ -1,9 +1,11 @@
 from operator import attrgetter
+from unittest import skipUnless
 
 from django.core.exceptions import FieldError, ValidationError
 from django.db import connection, models
 from django.test import SimpleTestCase, TestCase
 from django.test.utils import CaptureQueriesContext, isolate_apps
+from django.utils.version import PY37
 
 from .models import (
     Base, Chef, CommonInfo, GrandChild, GrandParent, ItalianRestaurant,
@@ -217,6 +219,12 @@ class ModelInheritanceTests(TestCase):
         self.assertSequenceEqual(qs, [p2, p1])
         self.assertIn(expected_order_by_sql, str(qs.query))
 
+    @skipUnless(PY37, '__class_getitem__() was added in Python 3.7')
+    def test_queryset_class_getitem(self):
+        self.assertIs(models.QuerySet[Post], models.QuerySet)
+        self.assertIs(models.QuerySet[Post, Post], models.QuerySet)
+        self.assertIs(models.QuerySet[Post, int, str], models.QuerySet)
+
 
 class ModelInheritanceDataTests(TestCase):
     @classmethod