make [Base]ExceptionGroup generic types

Author: iritkatriel

Lib/test/test_exception_group.py

@@ -10,6 +10,11 @@ def test_exception_group_types(self):
         self.assertTrue(issubclass(ExceptionGroup, BaseExceptionGroup))
         self.assertTrue(issubclass(BaseExceptionGroup, BaseException))
 
+    def test_exception_group_is_generic_type(self):
+        E = OSError
+        self.assertIsInstance(ExceptionGroup[E], types.GenericAlias)
+        self.assertIsInstance(BaseExceptionGroup[E], types.GenericAlias)
+
 
 class BadConstructorArgs(unittest.TestCase):
     def test_bad_EG_construction__too_many_args(self):

Objects/exceptions.c

@@ -1040,6 +1040,8 @@ static PyMemberDef BaseExceptionGroup_members[] = {
 };
 
 static PyMethodDef BaseExceptionGroup_methods[] = {
+    {"__class_getitem__", (PyCFunction)Py_GenericAlias,
+      METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
     {"derive", (PyCFunction)BaseExceptionGroup_derive, METH_VARARGS},
     {"split", (PyCFunction)BaseExceptionGroup_split, METH_VARARGS},
     {"subgroup", (PyCFunction)BaseExceptionGroup_subgroup, METH_VARARGS},