From 83552a67e60a422234db564942f5053ab1576ed4 Mon Sep 17 00:00:00 2001
From: Prakash Sellathurai <prakashsellathurai@gmail.com>
Date: Sat, 18 Apr 2026 05:51:13 +0530
Subject: [PATCH 1/3] [3.13]  gh-148222: Fix NULL dereference bugs in
 genericaliasobject.c (#148226)

(cherry picked from commit 634568d030f18183212c01bd4544aa7f97e05442)
---
 ...-04-07-20-37-23.gh-issue-148222.uF4D4E.rst |    1 +
 Objects/genericaliasobject.c                  | 2073 ++++++++---------
 2 files changed, 1037 insertions(+), 1037 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst
new file mode 100644
index 00000000000000..2c273fc4daba3d
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst
@@ -0,0 +1 @@
+Fix vectorcall support in :class:`types.GenericAlias` when the underlying type does not support the vectorcall protocol. Fix possible leaks in :class:`types.GenericAlias` and :class:`types.UnionType` in case of memory error.
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 8e59b3884cf529..3af8f349074eec 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -1,1037 +1,1036 @@
-// types.GenericAlias -- used to represent e.g. list[int].
-
-#include "Python.h"
-#include "pycore_ceval.h"         // _PyEval_GetBuiltin()
-#include "pycore_modsupport.h"    // _PyArg_NoKeywords()
-#include "pycore_object.h"
-#include "pycore_unionobject.h"   // _Py_union_type_or, _PyGenericAlias_Check
-#include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
-
-
-#include <stdbool.h>
-
-typedef struct {
-    PyObject_HEAD
-    PyObject *origin;
-    PyObject *args;
-    PyObject *parameters;
-    PyObject *weakreflist;
-    // Whether we're a starred type, e.g. *tuple[int].
-    bool starred;
-    vectorcallfunc vectorcall;
-} gaobject;
-
-typedef struct {
-    PyObject_HEAD
-    PyObject *obj;  /* Set to NULL when iterator is exhausted */
-} gaiterobject;
-
-static void
-ga_dealloc(PyObject *self)
-{
-    gaobject *alias = (gaobject *)self;
-
-    _PyObject_GC_UNTRACK(self);
-    FT_CLEAR_WEAKREFS((PyObject *)alias, alias->weakreflist);
-    Py_XDECREF(alias->origin);
-    Py_XDECREF(alias->args);
-    Py_XDECREF(alias->parameters);
-    Py_TYPE(self)->tp_free(self);
-}
-
-static int
-ga_traverse(PyObject *self, visitproc visit, void *arg)
-{
-    gaobject *alias = (gaobject *)self;
-    Py_VISIT(alias->origin);
-    Py_VISIT(alias->args);
-    Py_VISIT(alias->parameters);
-    return 0;
-}
-
-static int
-ga_repr_item(_PyUnicodeWriter *writer, PyObject *p)
-{
-    PyObject *qualname = NULL;
-    PyObject *module = NULL;
-    PyObject *r = NULL;
-    int rc;
-
-    if (p == Py_Ellipsis) {
-        // The Ellipsis object
-        r = PyUnicode_FromString("...");
-        goto done;
-    }
-
-    if ((rc = PyObject_HasAttrWithError(p, &_Py_ID(__origin__))) > 0 &&
-        (rc = PyObject_HasAttrWithError(p, &_Py_ID(__args__))) > 0)
-    {
-        // It looks like a GenericAlias
-        goto use_repr;
-    }
-    if (rc < 0) {
-        goto done;
-    }
-
-    if (PyObject_GetOptionalAttr(p, &_Py_ID(__qualname__), &qualname) < 0) {
-        goto done;
-    }
-    if (qualname == NULL) {
-        goto use_repr;
-    }
-    if (PyObject_GetOptionalAttr(p, &_Py_ID(__module__), &module) < 0) {
-        goto done;
-    }
-    if (module == NULL || module == Py_None) {
-        goto use_repr;
-    }
-
-    // Looks like a class
-    if (PyUnicode_Check(module) &&
-        _PyUnicode_EqualToASCIIString(module, "builtins"))
-    {
-        // builtins don't need a module name
-        r = PyObject_Str(qualname);
-        goto done;
-    }
-    else {
-        r = PyUnicode_FromFormat("%S.%S", module, qualname);
-        goto done;
-    }
-
-use_repr:
-    r = PyObject_Repr(p);
-
-done:
-    Py_XDECREF(qualname);
-    Py_XDECREF(module);
-    if (r == NULL) {
-        // error if any of the above PyObject_Repr/PyUnicode_From* fail
-        rc = -1;
-    }
-    else {
-        rc = _PyUnicodeWriter_WriteStr(writer, r);
-        Py_DECREF(r);
-    }
-    return rc;
-}
-
-static int
-ga_repr_items_list(_PyUnicodeWriter *writer, PyObject *p)
-{
-    assert(PyList_CheckExact(p));
-
-    Py_ssize_t len = PyList_GET_SIZE(p);
-
-    if (_PyUnicodeWriter_WriteASCIIString(writer, "[", 1) < 0) {
-        return -1;
-    }
-
-    for (Py_ssize_t i = 0; i < len; i++) {
-        if (i > 0) {
-            if (_PyUnicodeWriter_WriteASCIIString(writer, ", ", 2) < 0) {
-                return -1;
-            }
-        }
-        PyObject *item = PyList_GetItemRef(p, i);
-        if (item == NULL) {
-            return -1;  // list can be mutated in a callback
-        }
-        if (ga_repr_item(writer, item) < 0) {
-            Py_DECREF(item);
-            return -1;
-        }
-        Py_DECREF(item);
-    }
-
-    if (_PyUnicodeWriter_WriteASCIIString(writer, "]", 1) < 0) {
-        return -1;
-    }
-
-    return 0;
-}
-
-static PyObject *
-ga_repr(PyObject *self)
-{
-    gaobject *alias = (gaobject *)self;
-    Py_ssize_t len = PyTuple_GET_SIZE(alias->args);
-
-    _PyUnicodeWriter writer;
-    _PyUnicodeWriter_Init(&writer);
-
-    if (alias->starred) {
-        if (_PyUnicodeWriter_WriteASCIIString(&writer, "*", 1) < 0) {
-            goto error;
-        }
-    }
-    if (ga_repr_item(&writer, alias->origin) < 0) {
-        goto error;
-    }
-    if (_PyUnicodeWriter_WriteASCIIString(&writer, "[", 1) < 0) {
-        goto error;
-    }
-    for (Py_ssize_t i = 0; i < len; i++) {
-        if (i > 0) {
-            if (_PyUnicodeWriter_WriteASCIIString(&writer, ", ", 2) < 0) {
-                goto error;
-            }
-        }
-        PyObject *p = PyTuple_GET_ITEM(alias->args, i);
-        if (PyList_CheckExact(p)) {
-            // Looks like we are working with ParamSpec's list of type args:
-            if (ga_repr_items_list(&writer, p) < 0) {
-                goto error;
-            }
-        }
-        else if (ga_repr_item(&writer, p) < 0) {
-            goto error;
-        }
-    }
-    if (len == 0) {
-        // for something like tuple[()] we should print a "()"
-        if (_PyUnicodeWriter_WriteASCIIString(&writer, "()", 2) < 0) {
-            goto error;
-        }
-    }
-    if (_PyUnicodeWriter_WriteASCIIString(&writer, "]", 1) < 0) {
-        goto error;
-    }
-    return _PyUnicodeWriter_Finish(&writer);
-error:
-    _PyUnicodeWriter_Dealloc(&writer);
-    return NULL;
-}
-
-// Index of item in self[:len], or -1 if not found (self is a tuple)
-static Py_ssize_t
-tuple_index(PyObject *self, Py_ssize_t len, PyObject *item)
-{
-    for (Py_ssize_t i = 0; i < len; i++) {
-        if (PyTuple_GET_ITEM(self, i) == item) {
-            return i;
-        }
-    }
-    return -1;
-}
-
-static int
-tuple_add(PyObject *self, Py_ssize_t len, PyObject *item)
-{
-    if (tuple_index(self, len, item) < 0) {
-        PyTuple_SET_ITEM(self, len, Py_NewRef(item));
-        return 1;
-    }
-    return 0;
-}
-
-static Py_ssize_t
-tuple_extend(PyObject **dst, Py_ssize_t dstindex,
-             PyObject **src, Py_ssize_t count)
-{
-    assert(count >= 0);
-    if (_PyTuple_Resize(dst, PyTuple_GET_SIZE(*dst) + count - 1) != 0) {
-        return -1;
-    }
-    assert(dstindex + count <= PyTuple_GET_SIZE(*dst));
-    for (Py_ssize_t i = 0; i < count; ++i) {
-        PyObject *item = src[i];
-        PyTuple_SET_ITEM(*dst, dstindex + i, Py_NewRef(item));
-    }
-    return dstindex + count;
-}
-
-PyObject *
-_Py_make_parameters(PyObject *args)
-{
-    Py_ssize_t nargs = PyTuple_GET_SIZE(args);
-    Py_ssize_t len = nargs;
-    PyObject *parameters = PyTuple_New(len);
-    if (parameters == NULL)
-        return NULL;
-    Py_ssize_t iparam = 0;
-    for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
-        PyObject *t = PyTuple_GET_ITEM(args, iarg);
-        // We don't want __parameters__ descriptor of a bare Python class.
-        if (PyType_Check(t)) {
-            continue;
-        }
-        int rc = PyObject_HasAttrWithError(t, &_Py_ID(__typing_subst__));
-        if (rc < 0) {
-            Py_DECREF(parameters);
-            return NULL;
-        }
-        if (rc) {
-            iparam += tuple_add(parameters, iparam, t);
-        }
-        else {
-            PyObject *subparams;
-            if (PyObject_GetOptionalAttr(t, &_Py_ID(__parameters__),
-                                     &subparams) < 0) {
-                Py_DECREF(parameters);
-                return NULL;
-            }
-            if (subparams && PyTuple_Check(subparams)) {
-                Py_ssize_t len2 = PyTuple_GET_SIZE(subparams);
-                Py_ssize_t needed = len2 - 1 - (iarg - iparam);
-                if (needed > 0) {
-                    len += needed;
-                    if (_PyTuple_Resize(&parameters, len) < 0) {
-                        Py_DECREF(subparams);
-                        Py_DECREF(parameters);
-                        return NULL;
-                    }
-                }
-                for (Py_ssize_t j = 0; j < len2; j++) {
-                    PyObject *t2 = PyTuple_GET_ITEM(subparams, j);
-                    iparam += tuple_add(parameters, iparam, t2);
-                }
-            }
-            Py_XDECREF(subparams);
-        }
-    }
-    if (iparam < len) {
-        if (_PyTuple_Resize(&parameters, iparam) < 0) {
-            Py_XDECREF(parameters);
-            return NULL;
-        }
-    }
-    return parameters;
-}
-
-/* If obj is a generic alias, substitute type variables params
-   with substitutions argitems.  For example, if obj is list[T],
-   params is (T, S), and argitems is (str, int), return list[str].
-   If obj doesn't have a __parameters__ attribute or that's not
-   a non-empty tuple, return a new reference to obj. */
-static PyObject *
-subs_tvars(PyObject *obj, PyObject *params,
-           PyObject **argitems, Py_ssize_t nargs)
-{
-    PyObject *subparams;
-    if (PyObject_GetOptionalAttr(obj, &_Py_ID(__parameters__), &subparams) < 0) {
-        return NULL;
-    }
-    if (subparams && PyTuple_Check(subparams) && PyTuple_GET_SIZE(subparams)) {
-        Py_ssize_t nparams = PyTuple_GET_SIZE(params);
-        Py_ssize_t nsubargs = PyTuple_GET_SIZE(subparams);
-        PyObject *subargs = PyTuple_New(nsubargs);
-        if (subargs == NULL) {
-            Py_DECREF(subparams);
-            return NULL;
-        }
-        Py_ssize_t j = 0;
-        for (Py_ssize_t i = 0; i < nsubargs; ++i) {
-            PyObject *arg = PyTuple_GET_ITEM(subparams, i);
-            Py_ssize_t iparam = tuple_index(params, nparams, arg);
-            if (iparam >= 0) {
-                PyObject *param = PyTuple_GET_ITEM(params, iparam);
-                arg = argitems[iparam];
-                if (Py_TYPE(param)->tp_iter && PyTuple_Check(arg)) {  // TypeVarTuple
-                    j = tuple_extend(&subargs, j,
-                                    &PyTuple_GET_ITEM(arg, 0),
-                                    PyTuple_GET_SIZE(arg));
-                    if (j < 0) {
-                        return NULL;
-                    }
-                    continue;
-                }
-            }
-            PyTuple_SET_ITEM(subargs, j, Py_NewRef(arg));
-            j++;
-        }
-        assert(j == PyTuple_GET_SIZE(subargs));
-
-        obj = PyObject_GetItem(obj, subargs);
-
-        Py_DECREF(subargs);
-    }
-    else {
-        Py_INCREF(obj);
-    }
-    Py_XDECREF(subparams);
-    return obj;
-}
-
-static int
-_is_unpacked_typevartuple(PyObject *arg)
-{
-    PyObject *tmp;
-    if (PyType_Check(arg)) { // TODO: Add test
-        return 0;
-    }
-    int res = PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_is_unpacked_typevartuple__), &tmp);
-    if (res > 0) {
-        res = PyObject_IsTrue(tmp);
-        Py_DECREF(tmp);
-    }
-    return res;
-}
-
-static PyObject *
-_unpacked_tuple_args(PyObject *arg)
-{
-    PyObject *result;
-    assert(!PyType_Check(arg));
-    // Fast path
-    if (_PyGenericAlias_Check(arg) &&
-            ((gaobject *)arg)->starred &&
-            ((gaobject *)arg)->origin == (PyObject *)&PyTuple_Type)
-    {
-        result = ((gaobject *)arg)->args;
-        return Py_NewRef(result);
-    }
-
-    if (PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_unpacked_tuple_args__), &result) > 0) {
-        if (result == Py_None) {
-            Py_DECREF(result);
-            return NULL;
-        }
-        return result;
-    }
-    return NULL;
-}
-
-static PyObject *
-_unpack_args(PyObject *item)
-{
-    PyObject *newargs = PyList_New(0);
-    if (newargs == NULL) {
-        return NULL;
-    }
-    int is_tuple = PyTuple_Check(item);
-    Py_ssize_t nitems = is_tuple ? PyTuple_GET_SIZE(item) : 1;
-    PyObject **argitems = is_tuple ? &PyTuple_GET_ITEM(item, 0) : &item;
-    for (Py_ssize_t i = 0; i < nitems; i++) {
-        item = argitems[i];
-        if (!PyType_Check(item)) {
-            PyObject *subargs = _unpacked_tuple_args(item);
-            if (subargs != NULL &&
-                PyTuple_Check(subargs) &&
-                !(PyTuple_GET_SIZE(subargs) &&
-                  PyTuple_GET_ITEM(subargs, PyTuple_GET_SIZE(subargs)-1) == Py_Ellipsis))
-            {
-                if (PyList_SetSlice(newargs, PY_SSIZE_T_MAX, PY_SSIZE_T_MAX, subargs) < 0) {
-                    Py_DECREF(subargs);
-                    Py_DECREF(newargs);
-                    return NULL;
-                }
-                Py_DECREF(subargs);
-                continue;
-            }
-            Py_XDECREF(subargs);
-            if (PyErr_Occurred()) {
-                Py_DECREF(newargs);
-                return NULL;
-            }
-        }
-        if (PyList_Append(newargs, item) < 0) {
-            Py_DECREF(newargs);
-            return NULL;
-        }
-    }
-    Py_SETREF(newargs, PySequence_Tuple(newargs));
-    return newargs;
-}
-
-PyObject *
-_Py_subs_parameters(PyObject *self, PyObject *args, PyObject *parameters, PyObject *item)
-{
-    Py_ssize_t nparams = PyTuple_GET_SIZE(parameters);
-    if (nparams == 0) {
-        return PyErr_Format(PyExc_TypeError,
-                            "%R is not a generic class",
-                            self);
-    }
-    item = _unpack_args(item);
-    for (Py_ssize_t i = 0; i < nparams; i++) {
-        PyObject *param = PyTuple_GET_ITEM(parameters, i);
-        PyObject *prepare, *tmp;
-        if (PyObject_GetOptionalAttr(param, &_Py_ID(__typing_prepare_subst__), &prepare) < 0) {
-            Py_DECREF(item);
-            return NULL;
-        }
-        if (prepare && prepare != Py_None) {
-            if (PyTuple_Check(item)) {
-                tmp = PyObject_CallFunction(prepare, "OO", self, item);
-            }
-            else {
-                tmp = PyObject_CallFunction(prepare, "O(O)", self, item);
-            }
-            Py_DECREF(prepare);
-            Py_SETREF(item, tmp);
-            if (item == NULL) {
-                return NULL;
-            }
-        }
-    }
-    int is_tuple = PyTuple_Check(item);
-    Py_ssize_t nitems = is_tuple ? PyTuple_GET_SIZE(item) : 1;
-    PyObject **argitems = is_tuple ? &PyTuple_GET_ITEM(item, 0) : &item;
-    if (nitems != nparams) {
-        Py_DECREF(item);
-        return PyErr_Format(PyExc_TypeError,
-                            "Too %s arguments for %R; actual %zd, expected %zd",
-                            nitems > nparams ? "many" : "few",
-                            self, nitems, nparams);
-    }
-    /* Replace all type variables (specified by parameters)
-       with corresponding values specified by argitems.
-        t = list[T];          t[int]      -> newargs = [int]
-        t = dict[str, T];     t[int]      -> newargs = [str, int]
-        t = dict[T, list[S]]; t[str, int] -> newargs = [str, list[int]]
-     */
-    Py_ssize_t nargs = PyTuple_GET_SIZE(args);
-    PyObject *newargs = PyTuple_New(nargs);
-    if (newargs == NULL) {
-        Py_DECREF(item);
-        return NULL;
-    }
-    for (Py_ssize_t iarg = 0, jarg = 0; iarg < nargs; iarg++) {
-        PyObject *arg = PyTuple_GET_ITEM(args, iarg);
-        if (PyType_Check(arg)) {
-            PyTuple_SET_ITEM(newargs, jarg, Py_NewRef(arg));
-            jarg++;
-            continue;
-        }
-
-        int unpack = _is_unpacked_typevartuple(arg);
-        if (unpack < 0) {
-            Py_DECREF(newargs);
-            Py_DECREF(item);
-            return NULL;
-        }
-        PyObject *subst;
-        if (PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_subst__), &subst) < 0) {
-            Py_DECREF(newargs);
-            Py_DECREF(item);
-            return NULL;
-        }
-        if (subst) {
-            Py_ssize_t iparam = tuple_index(parameters, nparams, arg);
-            assert(iparam >= 0);
-            arg = PyObject_CallOneArg(subst, argitems[iparam]);
-            Py_DECREF(subst);
-        }
-        else {
-            arg = subs_tvars(arg, parameters, argitems, nitems);
-        }
-        if (arg == NULL) {
-            Py_DECREF(newargs);
-            Py_DECREF(item);
-            return NULL;
-        }
-        if (unpack) {
-            if (!PyTuple_Check(arg)) {
-                Py_DECREF(newargs);
-                Py_DECREF(item);
-                PyObject *original = PyTuple_GET_ITEM(args, iarg);
-                PyErr_Format(PyExc_TypeError,
-                             "expected __typing_subst__ of %T objects to return a tuple, not %T",
-                             original, arg);
-                Py_DECREF(arg);
-                return NULL;
-            }
-            jarg = tuple_extend(&newargs, jarg,
-                    &PyTuple_GET_ITEM(arg, 0), PyTuple_GET_SIZE(arg));
-            Py_DECREF(arg);
-            if (jarg < 0) {
-                Py_DECREF(item);
-                assert(newargs == NULL);
-                return NULL;
-            }
-        }
-        else {
-            PyTuple_SET_ITEM(newargs, jarg, arg);
-            jarg++;
-        }
-    }
-
-    Py_DECREF(item);
-    return newargs;
-}
-
-PyDoc_STRVAR(genericalias__doc__,
-"GenericAlias(origin, args, /)\n"
-"--\n\n"
-"Represent a PEP 585 generic type\n"
-"\n"
-"E.g. for t = list[int], t.__origin__ is list and t.__args__ is (int,).");
-
-static PyObject *
-ga_getitem(PyObject *self, PyObject *item)
-{
-    gaobject *alias = (gaobject *)self;
-    // Populate __parameters__ if needed.
-    if (alias->parameters == NULL) {
-        alias->parameters = _Py_make_parameters(alias->args);
-        if (alias->parameters == NULL) {
-            return NULL;
-        }
-    }
-
-    PyObject *newargs = _Py_subs_parameters(self, alias->args, alias->parameters, item);
-    if (newargs == NULL) {
-        return NULL;
-    }
-
-    PyObject *res = Py_GenericAlias(alias->origin, newargs);
-    if (res == NULL) {
-        Py_DECREF(newargs);
-        return NULL;
-    }
-    ((gaobject *)res)->starred = alias->starred;
-
-    Py_DECREF(newargs);
-    return res;
-}
-
-static PyMappingMethods ga_as_mapping = {
-    .mp_subscript = ga_getitem,
-};
-
-static Py_hash_t
-ga_hash(PyObject *self)
-{
-    gaobject *alias = (gaobject *)self;
-    // TODO: Hash in the hash for the origin
-    Py_hash_t h0 = PyObject_Hash(alias->origin);
-    if (h0 == -1) {
-        return -1;
-    }
-    Py_hash_t h1 = PyObject_Hash(alias->args);
-    if (h1 == -1) {
-        return -1;
-    }
-    return h0 ^ h1;
-}
-
-static inline PyObject *
-set_orig_class(PyObject *obj, PyObject *self)
-{
-    if (obj != NULL) {
-        if (PyObject_SetAttr(obj, &_Py_ID(__orig_class__), self) < 0) {
-            if (!PyErr_ExceptionMatches(PyExc_AttributeError) &&
-                !PyErr_ExceptionMatches(PyExc_TypeError))
-            {
-                Py_DECREF(obj);
-                return NULL;
-            }
-            PyErr_Clear();
-        }
-    }
-    return obj;
-}
-
-static PyObject *
-ga_call(PyObject *self, PyObject *args, PyObject *kwds)
-{
-    gaobject *alias = (gaobject *)self;
-    PyObject *obj = PyObject_Call(alias->origin, args, kwds);
-    return set_orig_class(obj, self);
-}
-
-static PyObject *
-ga_vectorcall(PyObject *self, PyObject *const *args,
-              size_t nargsf, PyObject *kwnames)
-{
-    gaobject *alias = (gaobject *) self;
-    PyObject *obj = PyVectorcall_Function(alias->origin)(alias->origin, args, nargsf, kwnames);
-    return set_orig_class(obj, self);
-}
-
-static const char* const attr_exceptions[] = {
-    "__class__",
-    "__origin__",
-    "__args__",
-    "__unpacked__",
-    "__parameters__",
-    "__typing_unpacked_tuple_args__",
-    "__mro_entries__",
-    "__reduce_ex__",  // needed so we don't look up object.__reduce_ex__
-    "__reduce__",
-    NULL,
-};
-
-static const char* const attr_blocked[] = {
-    "__bases__",
-    "__copy__",
-    "__deepcopy__",
-    NULL,
-};
-
-static PyObject *
-ga_getattro(PyObject *self, PyObject *name)
-{
-    gaobject *alias = (gaobject *)self;
-    if (PyUnicode_Check(name)) {
-        // When we check blocked attrs, we don't allow to proxy them to `__origin__`.
-        // Otherwise, we can break existing code.
-        for (const char * const *p = attr_blocked; ; p++) {
-            if (*p == NULL) {
-                break;
-            }
-            if (_PyUnicode_EqualToASCIIString(name, *p)) {
-                goto generic_getattr;
-            }
-        }
-
-        // When we see own attrs, it has a priority over `__origin__`'s attr.
-        for (const char * const *p = attr_exceptions; ; p++) {
-            if (*p == NULL) {
-                return PyObject_GetAttr(alias->origin, name);
-            }
-            if (_PyUnicode_EqualToASCIIString(name, *p)) {
-                goto generic_getattr;
-            }
-        }
-    }
-
-generic_getattr:
-    return PyObject_GenericGetAttr(self, name);
-}
-
-static PyObject *
-ga_richcompare(PyObject *a, PyObject *b, int op)
-{
-    if (!_PyGenericAlias_Check(b) ||
-        (op != Py_EQ && op != Py_NE))
-    {
-        Py_RETURN_NOTIMPLEMENTED;
-    }
-
-    if (op == Py_NE) {
-        PyObject *eq = ga_richcompare(a, b, Py_EQ);
-        if (eq == NULL)
-            return NULL;
-        Py_DECREF(eq);
-        if (eq == Py_True) {
-            Py_RETURN_FALSE;
-        }
-        else {
-            Py_RETURN_TRUE;
-        }
-    }
-
-    gaobject *aa = (gaobject *)a;
-    gaobject *bb = (gaobject *)b;
-    if (aa->starred != bb->starred) {
-        Py_RETURN_FALSE;
-    }
-    int eq = PyObject_RichCompareBool(aa->origin, bb->origin, Py_EQ);
-    if (eq < 0) {
-        return NULL;
-    }
-    if (!eq) {
-        Py_RETURN_FALSE;
-    }
-    return PyObject_RichCompare(aa->args, bb->args, Py_EQ);
-}
-
-static PyObject *
-ga_mro_entries(PyObject *self, PyObject *args)
-{
-    gaobject *alias = (gaobject *)self;
-    return PyTuple_Pack(1, alias->origin);
-}
-
-static PyObject *
-ga_instancecheck(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    PyErr_SetString(PyExc_TypeError,
-                    "isinstance() argument 2 cannot be a parameterized generic");
-    return NULL;
-}
-
-static PyObject *
-ga_subclasscheck(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    PyErr_SetString(PyExc_TypeError,
-                    "issubclass() argument 2 cannot be a parameterized generic");
-    return NULL;
-}
-
-static PyObject *
-ga_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    gaobject *alias = (gaobject *)self;
-    if (alias->starred) {
-        PyObject *tmp = Py_GenericAlias(alias->origin, alias->args);
-        if (tmp != NULL) {
-            Py_SETREF(tmp, PyObject_GetIter(tmp));
-        }
-        if (tmp == NULL) {
-            return NULL;
-        }
-        return Py_BuildValue("N(N)", _PyEval_GetBuiltin(&_Py_ID(next)), tmp);
-    }
-    return Py_BuildValue("O(OO)", Py_TYPE(alias),
-                         alias->origin, alias->args);
-}
-
-static PyObject *
-ga_dir(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    gaobject *alias = (gaobject *)self;
-    PyObject *dir = PyObject_Dir(alias->origin);
-    if (dir == NULL) {
-        return NULL;
-    }
-
-    PyObject *dir_entry = NULL;
-    for (const char * const *p = attr_exceptions; ; p++) {
-        if (*p == NULL) {
-            break;
-        }
-        else {
-            dir_entry = PyUnicode_FromString(*p);
-            if (dir_entry == NULL) {
-                goto error;
-            }
-            int contains = PySequence_Contains(dir, dir_entry);
-            if (contains < 0) {
-                goto error;
-            }
-            if (contains == 0 && PyList_Append(dir, dir_entry) < 0) {
-                goto error;
-            }
-
-            Py_CLEAR(dir_entry);
-        }
-    }
-    return dir;
-
-error:
-    Py_DECREF(dir);
-    Py_XDECREF(dir_entry);
-    return NULL;
-}
-
-static PyMethodDef ga_methods[] = {
-    {"__mro_entries__", ga_mro_entries, METH_O},
-    {"__instancecheck__", ga_instancecheck, METH_O},
-    {"__subclasscheck__", ga_subclasscheck, METH_O},
-    {"__reduce__", ga_reduce, METH_NOARGS},
-    {"__dir__", ga_dir, METH_NOARGS},
-    {0}
-};
-
-static PyMemberDef ga_members[] = {
-    {"__origin__", _Py_T_OBJECT, offsetof(gaobject, origin), Py_READONLY},
-    {"__args__", _Py_T_OBJECT, offsetof(gaobject, args), Py_READONLY},
-    {"__unpacked__", Py_T_BOOL, offsetof(gaobject, starred), Py_READONLY},
-    {0}
-};
-
-static PyObject *
-ga_parameters(PyObject *self, void *unused)
-{
-    gaobject *alias = (gaobject *)self;
-    if (alias->parameters == NULL) {
-        alias->parameters = _Py_make_parameters(alias->args);
-        if (alias->parameters == NULL) {
-            return NULL;
-        }
-    }
-    return Py_NewRef(alias->parameters);
-}
-
-static PyObject *
-ga_unpacked_tuple_args(PyObject *self, void *unused)
-{
-    gaobject *alias = (gaobject *)self;
-    if (alias->starred && alias->origin == (PyObject *)&PyTuple_Type) {
-        return Py_NewRef(alias->args);
-    }
-    Py_RETURN_NONE;
-}
-
-static PyGetSetDef ga_properties[] = {
-    {"__parameters__", ga_parameters, (setter)NULL, PyDoc_STR("Type variables in the GenericAlias."), NULL},
-    {"__typing_unpacked_tuple_args__", ga_unpacked_tuple_args, (setter)NULL, NULL},
-    {0}
-};
-
-/* A helper function to create GenericAlias' args tuple and set its attributes.
- * Returns 1 on success, 0 on failure.
- */
-static inline int
-setup_ga(gaobject *alias, PyObject *origin, PyObject *args) {
-    if (!PyTuple_Check(args)) {
-        args = PyTuple_Pack(1, args);
-        if (args == NULL) {
-            return 0;
-        }
-    }
-    else {
-        Py_INCREF(args);
-    }
-
-    alias->origin = Py_NewRef(origin);
-    alias->args = args;
-    alias->parameters = NULL;
-    alias->weakreflist = NULL;
-
-    if (PyVectorcall_Function(origin) != NULL) {
-        alias->vectorcall = ga_vectorcall;
-    }
-    else {
-        alias->vectorcall = NULL;
-    }
-
-    return 1;
-}
-
-static PyObject *
-ga_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
-{
-    if (!_PyArg_NoKeywords("GenericAlias", kwds)) {
-        return NULL;
-    }
-    if (!_PyArg_CheckPositional("GenericAlias", PyTuple_GET_SIZE(args), 2, 2)) {
-        return NULL;
-    }
-    PyObject *origin = PyTuple_GET_ITEM(args, 0);
-    PyObject *arguments = PyTuple_GET_ITEM(args, 1);
-    gaobject *self = (gaobject *)type->tp_alloc(type, 0);
-    if (self == NULL) {
-        return NULL;
-    }
-    if (!setup_ga(self, origin, arguments)) {
-        Py_DECREF(self);
-        return NULL;
-    }
-    return (PyObject *)self;
-}
-
-static PyNumberMethods ga_as_number = {
-        .nb_or = _Py_union_type_or, // Add __or__ function
-};
-
-static PyObject *
-ga_iternext(gaiterobject *gi) {
-    if (gi->obj == NULL) {
-        PyErr_SetNone(PyExc_StopIteration);
-        return NULL;
-    }
-    gaobject *alias = (gaobject *)gi->obj;
-    PyObject *starred_alias = Py_GenericAlias(alias->origin, alias->args);
-    if (starred_alias == NULL) {
-        return NULL;
-    }
-    ((gaobject *)starred_alias)->starred = true;
-    Py_SETREF(gi->obj, NULL);
-    return starred_alias;
-}
-
-static void
-ga_iter_dealloc(gaiterobject *gi) {
-    PyObject_GC_UnTrack(gi);
-    Py_XDECREF(gi->obj);
-    PyObject_GC_Del(gi);
-}
-
-static int
-ga_iter_traverse(gaiterobject *gi, visitproc visit, void *arg)
-{
-    Py_VISIT(gi->obj);
-    return 0;
-}
-
-static int
-ga_iter_clear(PyObject *self) {
-    gaiterobject *gi = (gaiterobject *)self;
-    Py_CLEAR(gi->obj);
-    return 0;
-}
-
-static PyObject *
-ga_iter_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    PyObject *iter = _PyEval_GetBuiltin(&_Py_ID(iter));
-    gaiterobject *gi = (gaiterobject *)self;
-
-    /* _PyEval_GetBuiltin can invoke arbitrary code,
-     * call must be before access of iterator pointers.
-     * see issue #101765 */
-
-    if (gi->obj)
-        return Py_BuildValue("N(O)", iter, gi->obj);
-    else
-        return Py_BuildValue("N(())", iter);
-}
-
-static PyMethodDef ga_iter_methods[] = {
-    {"__reduce__", ga_iter_reduce, METH_NOARGS},
-    {0}
-};
-
-// gh-91632: _Py_GenericAliasIterType is exported  to be cleared
-// in _PyTypes_FiniTypes.
-PyTypeObject _Py_GenericAliasIterType = {
-    PyVarObject_HEAD_INIT(&PyType_Type, 0)
-    .tp_name = "generic_alias_iterator",
-    .tp_basicsize = sizeof(gaiterobject),
-    .tp_iter = PyObject_SelfIter,
-    .tp_iternext = (iternextfunc)ga_iternext,
-    .tp_traverse = (traverseproc)ga_iter_traverse,
-    .tp_methods = ga_iter_methods,
-    .tp_dealloc = (destructor)ga_iter_dealloc,
-    .tp_clear = (inquiry)ga_iter_clear,
-    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
-};
-
-static PyObject *
-ga_iter(PyObject *self) {
-    gaiterobject *gi = PyObject_GC_New(gaiterobject, &_Py_GenericAliasIterType);
-    if (gi == NULL) {
-        return NULL;
-    }
-    gi->obj = Py_NewRef(self);
-    PyObject_GC_Track(gi);
-    return (PyObject *)gi;
-}
-
-// TODO:
-// - argument clinic?
-// - cache?
-PyTypeObject Py_GenericAliasType = {
-    PyVarObject_HEAD_INIT(&PyType_Type, 0)
-    .tp_name = "types.GenericAlias",
-    .tp_doc = genericalias__doc__,
-    .tp_basicsize = sizeof(gaobject),
-    .tp_dealloc = ga_dealloc,
-    .tp_repr = ga_repr,
-    .tp_as_number = &ga_as_number,  // allow X | Y of GenericAlias objs
-    .tp_as_mapping = &ga_as_mapping,
-    .tp_hash = ga_hash,
-    .tp_call = ga_call,
-    .tp_getattro = ga_getattro,
-    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_VECTORCALL,
-    .tp_traverse = ga_traverse,
-    .tp_richcompare = ga_richcompare,
-    .tp_weaklistoffset = offsetof(gaobject, weakreflist),
-    .tp_methods = ga_methods,
-    .tp_members = ga_members,
-    .tp_alloc = PyType_GenericAlloc,
-    .tp_new = ga_new,
-    .tp_free = PyObject_GC_Del,
-    .tp_getset = ga_properties,
-    .tp_iter = (getiterfunc)ga_iter,
-    .tp_vectorcall_offset = offsetof(gaobject, vectorcall),
-};
-
-PyObject *
-Py_GenericAlias(PyObject *origin, PyObject *args)
-{
-    gaobject *alias = (gaobject*) PyType_GenericAlloc(
-            (PyTypeObject *)&Py_GenericAliasType, 0);
-    if (alias == NULL) {
-        return NULL;
-    }
-    if (!setup_ga(alias, origin, args)) {
-        Py_DECREF(alias);
-        return NULL;
-    }
-    return (PyObject *)alias;
-}
+// types.GenericAlias -- used to represent e.g. list[int].
+
+#include "Python.h"
+#include "pycore_ceval.h"         // _PyEval_GetBuiltin()
+#include "pycore_modsupport.h"    // _PyArg_NoKeywords()
+#include "pycore_object.h"
+#include "pycore_unionobject.h"   // _Py_union_type_or, _PyGenericAlias_Check
+#include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
+
+
+#include <stdbool.h>
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *origin;
+    PyObject *args;
+    PyObject *parameters;
+    PyObject *weakreflist;
+    // Whether we're a starred type, e.g. *tuple[int].
+    bool starred;
+    vectorcallfunc vectorcall;
+} gaobject;
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *obj;  /* Set to NULL when iterator is exhausted */
+} gaiterobject;
+
+static void
+ga_dealloc(PyObject *self)
+{
+    gaobject *alias = (gaobject *)self;
+
+    _PyObject_GC_UNTRACK(self);
+    FT_CLEAR_WEAKREFS((PyObject *)alias, alias->weakreflist);
+    Py_XDECREF(alias->origin);
+    Py_XDECREF(alias->args);
+    Py_XDECREF(alias->parameters);
+    Py_TYPE(self)->tp_free(self);
+}
+
+static int
+ga_traverse(PyObject *self, visitproc visit, void *arg)
+{
+    gaobject *alias = (gaobject *)self;
+    Py_VISIT(alias->origin);
+    Py_VISIT(alias->args);
+    Py_VISIT(alias->parameters);
+    return 0;
+}
+
+static int
+ga_repr_item(_PyUnicodeWriter *writer, PyObject *p)
+{
+    PyObject *qualname = NULL;
+    PyObject *module = NULL;
+    PyObject *r = NULL;
+    int rc;
+
+    if (p == Py_Ellipsis) {
+        // The Ellipsis object
+        r = PyUnicode_FromString("...");
+        goto done;
+    }
+
+    if ((rc = PyObject_HasAttrWithError(p, &_Py_ID(__origin__))) > 0 &&
+        (rc = PyObject_HasAttrWithError(p, &_Py_ID(__args__))) > 0)
+    {
+        // It looks like a GenericAlias
+        goto use_repr;
+    }
+    if (rc < 0) {
+        goto done;
+    }
+
+    if (PyObject_GetOptionalAttr(p, &_Py_ID(__qualname__), &qualname) < 0) {
+        goto done;
+    }
+    if (qualname == NULL) {
+        goto use_repr;
+    }
+    if (PyObject_GetOptionalAttr(p, &_Py_ID(__module__), &module) < 0) {
+        goto done;
+    }
+    if (module == NULL || module == Py_None) {
+        goto use_repr;
+    }
+
+    // Looks like a class
+    if (PyUnicode_Check(module) &&
+        _PyUnicode_EqualToASCIIString(module, "builtins"))
+    {
+        // builtins don't need a module name
+        r = PyObject_Str(qualname);
+        goto done;
+    }
+    else {
+        r = PyUnicode_FromFormat("%S.%S", module, qualname);
+        goto done;
+    }
+
+use_repr:
+    r = PyObject_Repr(p);
+
+done:
+    Py_XDECREF(qualname);
+    Py_XDECREF(module);
+    if (r == NULL) {
+        // error if any of the above PyObject_Repr/PyUnicode_From* fail
+        rc = -1;
+    }
+    else {
+        rc = _PyUnicodeWriter_WriteStr(writer, r);
+        Py_DECREF(r);
+    }
+    return rc;
+}
+
+static int
+ga_repr_items_list(_PyUnicodeWriter *writer, PyObject *p)
+{
+    assert(PyList_CheckExact(p));
+
+    Py_ssize_t len = PyList_GET_SIZE(p);
+
+    if (_PyUnicodeWriter_WriteASCIIString(writer, "[", 1) < 0) {
+        return -1;
+    }
+
+    for (Py_ssize_t i = 0; i < len; i++) {
+        if (i > 0) {
+            if (_PyUnicodeWriter_WriteASCIIString(writer, ", ", 2) < 0) {
+                return -1;
+            }
+        }
+        PyObject *item = PyList_GetItemRef(p, i);
+        if (item == NULL) {
+            return -1;  // list can be mutated in a callback
+        }
+        if (ga_repr_item(writer, item) < 0) {
+            Py_DECREF(item);
+            return -1;
+        }
+        Py_DECREF(item);
+    }
+
+    if (_PyUnicodeWriter_WriteASCIIString(writer, "]", 1) < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static PyObject *
+ga_repr(PyObject *self)
+{
+    gaobject *alias = (gaobject *)self;
+    Py_ssize_t len = PyTuple_GET_SIZE(alias->args);
+
+    _PyUnicodeWriter writer;
+    _PyUnicodeWriter_Init(&writer);
+
+    if (alias->starred) {
+        if (_PyUnicodeWriter_WriteASCIIString(&writer, "*", 1) < 0) {
+            goto error;
+        }
+    }
+    if (ga_repr_item(&writer, alias->origin) < 0) {
+        goto error;
+    }
+    if (_PyUnicodeWriter_WriteASCIIString(&writer, "[", 1) < 0) {
+        goto error;
+    }
+    for (Py_ssize_t i = 0; i < len; i++) {
+        if (i > 0) {
+            if (_PyUnicodeWriter_WriteASCIIString(&writer, ", ", 2) < 0) {
+                goto error;
+            }
+        }
+        PyObject *p = PyTuple_GET_ITEM(alias->args, i);
+        if (PyList_CheckExact(p)) {
+            // Looks like we are working with ParamSpec's list of type args:
+            if (ga_repr_items_list(&writer, p) < 0) {
+                goto error;
+            }
+        }
+        else if (ga_repr_item(&writer, p) < 0) {
+            goto error;
+        }
+    }
+    if (len == 0) {
+        // for something like tuple[()] we should print a "()"
+        if (_PyUnicodeWriter_WriteASCIIString(&writer, "()", 2) < 0) {
+            goto error;
+        }
+    }
+    if (_PyUnicodeWriter_WriteASCIIString(&writer, "]", 1) < 0) {
+        goto error;
+    }
+    return _PyUnicodeWriter_Finish(&writer);
+error:
+    _PyUnicodeWriter_Dealloc(&writer);
+    return NULL;
+}
+
+// Index of item in self[:len], or -1 if not found (self is a tuple)
+static Py_ssize_t
+tuple_index(PyObject *self, Py_ssize_t len, PyObject *item)
+{
+    for (Py_ssize_t i = 0; i < len; i++) {
+        if (PyTuple_GET_ITEM(self, i) == item) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+static int
+tuple_add(PyObject *self, Py_ssize_t len, PyObject *item)
+{
+    if (tuple_index(self, len, item) < 0) {
+        PyTuple_SET_ITEM(self, len, Py_NewRef(item));
+        return 1;
+    }
+    return 0;
+}
+
+static Py_ssize_t
+tuple_extend(PyObject **dst, Py_ssize_t dstindex,
+             PyObject **src, Py_ssize_t count)
+{
+    assert(count >= 0);
+    if (_PyTuple_Resize(dst, PyTuple_GET_SIZE(*dst) + count - 1) != 0) {
+        return -1;
+    }
+    assert(dstindex + count <= PyTuple_GET_SIZE(*dst));
+    for (Py_ssize_t i = 0; i < count; ++i) {
+        PyObject *item = src[i];
+        PyTuple_SET_ITEM(*dst, dstindex + i, Py_NewRef(item));
+    }
+    return dstindex + count;
+}
+
+PyObject *
+_Py_make_parameters(PyObject *args)
+{
+    Py_ssize_t nargs = PyTuple_GET_SIZE(args);
+    Py_ssize_t len = nargs;
+    PyObject *parameters = PyTuple_New(len);
+    if (parameters == NULL)
+        return NULL;
+    Py_ssize_t iparam = 0;
+    for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
+        PyObject *t = PyTuple_GET_ITEM(args, iarg);
+        // We don't want __parameters__ descriptor of a bare Python class.
+        if (PyType_Check(t)) {
+            continue;
+        }
+        int rc = PyObject_HasAttrWithError(t, &_Py_ID(__typing_subst__));
+        if (rc < 0) {
+            Py_DECREF(parameters);
+            return NULL;
+        }
+        if (rc) {
+            iparam += tuple_add(parameters, iparam, t);
+        }
+        else {
+            PyObject *subparams;
+            if (PyObject_GetOptionalAttr(t, &_Py_ID(__parameters__),
+                                     &subparams) < 0) {
+                Py_DECREF(parameters);
+                return NULL;
+            }
+            if (subparams && PyTuple_Check(subparams)) {
+                Py_ssize_t len2 = PyTuple_GET_SIZE(subparams);
+                Py_ssize_t needed = len2 - 1 - (iarg - iparam);
+                if (needed > 0) {
+                    len += needed;
+                    if (_PyTuple_Resize(&parameters, len) < 0) {
+                        Py_DECREF(subparams);
+                        return NULL;
+                    }
+                }
+                for (Py_ssize_t j = 0; j < len2; j++) {
+                    PyObject *t2 = PyTuple_GET_ITEM(subparams, j);
+                    iparam += tuple_add(parameters, iparam, t2);
+                }
+            }
+            Py_XDECREF(subparams);
+        }
+    }
+    if (iparam < len) {
+        if (_PyTuple_Resize(&parameters, iparam) < 0) {
+            Py_XDECREF(parameters);
+            return NULL;
+        }
+    }
+    return parameters;
+}
+
+/* If obj is a generic alias, substitute type variables params
+   with substitutions argitems.  For example, if obj is list[T],
+   params is (T, S), and argitems is (str, int), return list[str].
+   If obj doesn't have a __parameters__ attribute or that's not
+   a non-empty tuple, return a new reference to obj. */
+static PyObject *
+subs_tvars(PyObject *obj, PyObject *params,
+           PyObject **argitems, Py_ssize_t nargs)
+{
+    PyObject *subparams;
+    if (PyObject_GetOptionalAttr(obj, &_Py_ID(__parameters__), &subparams) < 0) {
+        return NULL;
+    }
+    if (subparams && PyTuple_Check(subparams) && PyTuple_GET_SIZE(subparams)) {
+        Py_ssize_t nparams = PyTuple_GET_SIZE(params);
+        Py_ssize_t nsubargs = PyTuple_GET_SIZE(subparams);
+        PyObject *subargs = PyTuple_New(nsubargs);
+        if (subargs == NULL) {
+            Py_DECREF(subparams);
+            return NULL;
+        }
+        Py_ssize_t j = 0;
+        for (Py_ssize_t i = 0; i < nsubargs; ++i) {
+            PyObject *arg = PyTuple_GET_ITEM(subparams, i);
+            Py_ssize_t iparam = tuple_index(params, nparams, arg);
+            if (iparam >= 0) {
+                PyObject *param = PyTuple_GET_ITEM(params, iparam);
+                arg = argitems[iparam];
+                if (Py_TYPE(param)->tp_iter && PyTuple_Check(arg)) {  // TypeVarTuple
+                    j = tuple_extend(&subargs, j,
+                                    &PyTuple_GET_ITEM(arg, 0),
+                                    PyTuple_GET_SIZE(arg));
+                    if (j < 0) {
+                        return NULL;
+                    }
+                    continue;
+                }
+            }
+            PyTuple_SET_ITEM(subargs, j, Py_NewRef(arg));
+            j++;
+        }
+        assert(j == PyTuple_GET_SIZE(subargs));
+
+        obj = PyObject_GetItem(obj, subargs);
+
+        Py_DECREF(subargs);
+    }
+    else {
+        Py_INCREF(obj);
+    }
+    Py_XDECREF(subparams);
+    return obj;
+}
+
+static int
+_is_unpacked_typevartuple(PyObject *arg)
+{
+    PyObject *tmp;
+    if (PyType_Check(arg)) { // TODO: Add test
+        return 0;
+    }
+    int res = PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_is_unpacked_typevartuple__), &tmp);
+    if (res > 0) {
+        res = PyObject_IsTrue(tmp);
+        Py_DECREF(tmp);
+    }
+    return res;
+}
+
+static PyObject *
+_unpacked_tuple_args(PyObject *arg)
+{
+    PyObject *result;
+    assert(!PyType_Check(arg));
+    // Fast path
+    if (_PyGenericAlias_Check(arg) &&
+            ((gaobject *)arg)->starred &&
+            ((gaobject *)arg)->origin == (PyObject *)&PyTuple_Type)
+    {
+        result = ((gaobject *)arg)->args;
+        return Py_NewRef(result);
+    }
+
+    if (PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_unpacked_tuple_args__), &result) > 0) {
+        if (result == Py_None) {
+            Py_DECREF(result);
+            return NULL;
+        }
+        return result;
+    }
+    return NULL;
+}
+
+static PyObject *
+_unpack_args(PyObject *item)
+{
+    PyObject *newargs = PyList_New(0);
+    if (newargs == NULL) {
+        return NULL;
+    }
+    int is_tuple = PyTuple_Check(item);
+    Py_ssize_t nitems = is_tuple ? PyTuple_GET_SIZE(item) : 1;
+    PyObject **argitems = is_tuple ? &PyTuple_GET_ITEM(item, 0) : &item;
+    for (Py_ssize_t i = 0; i < nitems; i++) {
+        item = argitems[i];
+        if (!PyType_Check(item)) {
+            PyObject *subargs = _unpacked_tuple_args(item);
+            if (subargs != NULL &&
+                PyTuple_Check(subargs) &&
+                !(PyTuple_GET_SIZE(subargs) &&
+                  PyTuple_GET_ITEM(subargs, PyTuple_GET_SIZE(subargs)-1) == Py_Ellipsis))
+            {
+                if (PyList_SetSlice(newargs, PY_SSIZE_T_MAX, PY_SSIZE_T_MAX, subargs) < 0) {
+                    Py_DECREF(subargs);
+                    Py_DECREF(newargs);
+                    return NULL;
+                }
+                Py_DECREF(subargs);
+                continue;
+            }
+            Py_XDECREF(subargs);
+            if (PyErr_Occurred()) {
+                Py_DECREF(newargs);
+                return NULL;
+            }
+        }
+        if (PyList_Append(newargs, item) < 0) {
+            Py_DECREF(newargs);
+            return NULL;
+        }
+    }
+    Py_SETREF(newargs, PySequence_Tuple(newargs));
+    return newargs;
+}
+
+PyObject *
+_Py_subs_parameters(PyObject *self, PyObject *args, PyObject *parameters, PyObject *item)
+{
+    Py_ssize_t nparams = PyTuple_GET_SIZE(parameters);
+    if (nparams == 0) {
+        return PyErr_Format(PyExc_TypeError,
+                            "%R is not a generic class",
+                            self);
+    }
+    item = _unpack_args(item);
+    for (Py_ssize_t i = 0; i < nparams; i++) {
+        PyObject *param = PyTuple_GET_ITEM(parameters, i);
+        PyObject *prepare, *tmp;
+        if (PyObject_GetOptionalAttr(param, &_Py_ID(__typing_prepare_subst__), &prepare) < 0) {
+            Py_DECREF(item);
+            return NULL;
+        }
+        if (prepare && prepare != Py_None) {
+            if (PyTuple_Check(item)) {
+                tmp = PyObject_CallFunction(prepare, "OO", self, item);
+            }
+            else {
+                tmp = PyObject_CallFunction(prepare, "O(O)", self, item);
+            }
+            Py_DECREF(prepare);
+            Py_SETREF(item, tmp);
+            if (item == NULL) {
+                return NULL;
+            }
+        }
+    }
+    int is_tuple = PyTuple_Check(item);
+    Py_ssize_t nitems = is_tuple ? PyTuple_GET_SIZE(item) : 1;
+    PyObject **argitems = is_tuple ? &PyTuple_GET_ITEM(item, 0) : &item;
+    if (nitems != nparams) {
+        Py_DECREF(item);
+        return PyErr_Format(PyExc_TypeError,
+                            "Too %s arguments for %R; actual %zd, expected %zd",
+                            nitems > nparams ? "many" : "few",
+                            self, nitems, nparams);
+    }
+    /* Replace all type variables (specified by parameters)
+       with corresponding values specified by argitems.
+        t = list[T];          t[int]      -> newargs = [int]
+        t = dict[str, T];     t[int]      -> newargs = [str, int]
+        t = dict[T, list[S]]; t[str, int] -> newargs = [str, list[int]]
+     */
+    Py_ssize_t nargs = PyTuple_GET_SIZE(args);
+    PyObject *newargs = PyTuple_New(nargs);
+    if (newargs == NULL) {
+        Py_DECREF(item);
+        return NULL;
+    }
+    for (Py_ssize_t iarg = 0, jarg = 0; iarg < nargs; iarg++) {
+        PyObject *arg = PyTuple_GET_ITEM(args, iarg);
+        if (PyType_Check(arg)) {
+            PyTuple_SET_ITEM(newargs, jarg, Py_NewRef(arg));
+            jarg++;
+            continue;
+        }
+
+        int unpack = _is_unpacked_typevartuple(arg);
+        if (unpack < 0) {
+            Py_DECREF(newargs);
+            Py_DECREF(item);
+            return NULL;
+        }
+        PyObject *subst;
+        if (PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_subst__), &subst) < 0) {
+            Py_DECREF(newargs);
+            Py_DECREF(item);
+            return NULL;
+        }
+        if (subst) {
+            Py_ssize_t iparam = tuple_index(parameters, nparams, arg);
+            assert(iparam >= 0);
+            arg = PyObject_CallOneArg(subst, argitems[iparam]);
+            Py_DECREF(subst);
+        }
+        else {
+            arg = subs_tvars(arg, parameters, argitems, nitems);
+        }
+        if (arg == NULL) {
+            Py_DECREF(newargs);
+            Py_DECREF(item);
+            return NULL;
+        }
+        if (unpack) {
+            if (!PyTuple_Check(arg)) {
+                Py_DECREF(newargs);
+                Py_DECREF(item);
+                PyObject *original = PyTuple_GET_ITEM(args, iarg);
+                PyErr_Format(PyExc_TypeError,
+                             "expected __typing_subst__ of %T objects to return a tuple, not %T",
+                             original, arg);
+                Py_DECREF(arg);
+                return NULL;
+            }
+            jarg = tuple_extend(&newargs, jarg,
+                    &PyTuple_GET_ITEM(arg, 0), PyTuple_GET_SIZE(arg));
+            Py_DECREF(arg);
+            if (jarg < 0) {
+                Py_DECREF(item);
+                assert(newargs == NULL);
+                return NULL;
+            }
+        }
+        else {
+            PyTuple_SET_ITEM(newargs, jarg, arg);
+            jarg++;
+        }
+    }
+
+    Py_DECREF(item);
+    return newargs;
+}
+
+PyDoc_STRVAR(genericalias__doc__,
+"GenericAlias(origin, args, /)\n"
+"--\n\n"
+"Represent a PEP 585 generic type\n"
+"\n"
+"E.g. for t = list[int], t.__origin__ is list and t.__args__ is (int,).");
+
+static PyObject *
+ga_getitem(PyObject *self, PyObject *item)
+{
+    gaobject *alias = (gaobject *)self;
+    // Populate __parameters__ if needed.
+    if (alias->parameters == NULL) {
+        alias->parameters = _Py_make_parameters(alias->args);
+        if (alias->parameters == NULL) {
+            return NULL;
+        }
+    }
+
+    PyObject *newargs = _Py_subs_parameters(self, alias->args, alias->parameters, item);
+    if (newargs == NULL) {
+        return NULL;
+    }
+
+    PyObject *res = Py_GenericAlias(alias->origin, newargs);
+    if (res == NULL) {
+        Py_DECREF(newargs);
+        return NULL;
+    }
+    ((gaobject *)res)->starred = alias->starred;
+
+    Py_DECREF(newargs);
+    return res;
+}
+
+static PyMappingMethods ga_as_mapping = {
+    .mp_subscript = ga_getitem,
+};
+
+static Py_hash_t
+ga_hash(PyObject *self)
+{
+    gaobject *alias = (gaobject *)self;
+    // TODO: Hash in the hash for the origin
+    Py_hash_t h0 = PyObject_Hash(alias->origin);
+    if (h0 == -1) {
+        return -1;
+    }
+    Py_hash_t h1 = PyObject_Hash(alias->args);
+    if (h1 == -1) {
+        return -1;
+    }
+    return h0 ^ h1;
+}
+
+static inline PyObject *
+set_orig_class(PyObject *obj, PyObject *self)
+{
+    if (obj != NULL) {
+        if (PyObject_SetAttr(obj, &_Py_ID(__orig_class__), self) < 0) {
+            if (!PyErr_ExceptionMatches(PyExc_AttributeError) &&
+                !PyErr_ExceptionMatches(PyExc_TypeError))
+            {
+                Py_DECREF(obj);
+                return NULL;
+            }
+            PyErr_Clear();
+        }
+    }
+    return obj;
+}
+
+static PyObject *
+ga_call(PyObject *self, PyObject *args, PyObject *kwds)
+{
+    gaobject *alias = (gaobject *)self;
+    PyObject *obj = PyObject_Call(alias->origin, args, kwds);
+    return set_orig_class(obj, self);
+}
+
+static PyObject *
+ga_vectorcall(PyObject *self, PyObject *const *args,
+              size_t nargsf, PyObject *kwnames)
+{
+    gaobject *alias = (gaobject *) self;
+    PyObject *obj = PyObject_Vectorcall(alias->origin, args, nargsf, kwnames);
+    return set_orig_class(obj, self);
+}
+
+static const char* const attr_exceptions[] = {
+    "__class__",
+    "__origin__",
+    "__args__",
+    "__unpacked__",
+    "__parameters__",
+    "__typing_unpacked_tuple_args__",
+    "__mro_entries__",
+    "__reduce_ex__",  // needed so we don't look up object.__reduce_ex__
+    "__reduce__",
+    NULL,
+};
+
+static const char* const attr_blocked[] = {
+    "__bases__",
+    "__copy__",
+    "__deepcopy__",
+    NULL,
+};
+
+static PyObject *
+ga_getattro(PyObject *self, PyObject *name)
+{
+    gaobject *alias = (gaobject *)self;
+    if (PyUnicode_Check(name)) {
+        // When we check blocked attrs, we don't allow to proxy them to `__origin__`.
+        // Otherwise, we can break existing code.
+        for (const char * const *p = attr_blocked; ; p++) {
+            if (*p == NULL) {
+                break;
+            }
+            if (_PyUnicode_EqualToASCIIString(name, *p)) {
+                goto generic_getattr;
+            }
+        }
+
+        // When we see own attrs, it has a priority over `__origin__`'s attr.
+        for (const char * const *p = attr_exceptions; ; p++) {
+            if (*p == NULL) {
+                return PyObject_GetAttr(alias->origin, name);
+            }
+            if (_PyUnicode_EqualToASCIIString(name, *p)) {
+                goto generic_getattr;
+            }
+        }
+    }
+
+generic_getattr:
+    return PyObject_GenericGetAttr(self, name);
+}
+
+static PyObject *
+ga_richcompare(PyObject *a, PyObject *b, int op)
+{
+    if (!_PyGenericAlias_Check(b) ||
+        (op != Py_EQ && op != Py_NE))
+    {
+        Py_RETURN_NOTIMPLEMENTED;
+    }
+
+    if (op == Py_NE) {
+        PyObject *eq = ga_richcompare(a, b, Py_EQ);
+        if (eq == NULL)
+            return NULL;
+        Py_DECREF(eq);
+        if (eq == Py_True) {
+            Py_RETURN_FALSE;
+        }
+        else {
+            Py_RETURN_TRUE;
+        }
+    }
+
+    gaobject *aa = (gaobject *)a;
+    gaobject *bb = (gaobject *)b;
+    if (aa->starred != bb->starred) {
+        Py_RETURN_FALSE;
+    }
+    int eq = PyObject_RichCompareBool(aa->origin, bb->origin, Py_EQ);
+    if (eq < 0) {
+        return NULL;
+    }
+    if (!eq) {
+        Py_RETURN_FALSE;
+    }
+    return PyObject_RichCompare(aa->args, bb->args, Py_EQ);
+}
+
+static PyObject *
+ga_mro_entries(PyObject *self, PyObject *args)
+{
+    gaobject *alias = (gaobject *)self;
+    return PyTuple_Pack(1, alias->origin);
+}
+
+static PyObject *
+ga_instancecheck(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    PyErr_SetString(PyExc_TypeError,
+                    "isinstance() argument 2 cannot be a parameterized generic");
+    return NULL;
+}
+
+static PyObject *
+ga_subclasscheck(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    PyErr_SetString(PyExc_TypeError,
+                    "issubclass() argument 2 cannot be a parameterized generic");
+    return NULL;
+}
+
+static PyObject *
+ga_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    gaobject *alias = (gaobject *)self;
+    if (alias->starred) {
+        PyObject *tmp = Py_GenericAlias(alias->origin, alias->args);
+        if (tmp != NULL) {
+            Py_SETREF(tmp, PyObject_GetIter(tmp));
+        }
+        if (tmp == NULL) {
+            return NULL;
+        }
+        return Py_BuildValue("N(N)", _PyEval_GetBuiltin(&_Py_ID(next)), tmp);
+    }
+    return Py_BuildValue("O(OO)", Py_TYPE(alias),
+                         alias->origin, alias->args);
+}
+
+static PyObject *
+ga_dir(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    gaobject *alias = (gaobject *)self;
+    PyObject *dir = PyObject_Dir(alias->origin);
+    if (dir == NULL) {
+        return NULL;
+    }
+
+    PyObject *dir_entry = NULL;
+    for (const char * const *p = attr_exceptions; ; p++) {
+        if (*p == NULL) {
+            break;
+        }
+        else {
+            dir_entry = PyUnicode_FromString(*p);
+            if (dir_entry == NULL) {
+                goto error;
+            }
+            int contains = PySequence_Contains(dir, dir_entry);
+            if (contains < 0) {
+                goto error;
+            }
+            if (contains == 0 && PyList_Append(dir, dir_entry) < 0) {
+                goto error;
+            }
+
+            Py_CLEAR(dir_entry);
+        }
+    }
+    return dir;
+
+error:
+    Py_DECREF(dir);
+    Py_XDECREF(dir_entry);
+    return NULL;
+}
+
+static PyMethodDef ga_methods[] = {
+    {"__mro_entries__", ga_mro_entries, METH_O},
+    {"__instancecheck__", ga_instancecheck, METH_O},
+    {"__subclasscheck__", ga_subclasscheck, METH_O},
+    {"__reduce__", ga_reduce, METH_NOARGS},
+    {"__dir__", ga_dir, METH_NOARGS},
+    {0}
+};
+
+static PyMemberDef ga_members[] = {
+    {"__origin__", _Py_T_OBJECT, offsetof(gaobject, origin), Py_READONLY},
+    {"__args__", _Py_T_OBJECT, offsetof(gaobject, args), Py_READONLY},
+    {"__unpacked__", Py_T_BOOL, offsetof(gaobject, starred), Py_READONLY},
+    {0}
+};
+
+static PyObject *
+ga_parameters(PyObject *self, void *unused)
+{
+    gaobject *alias = (gaobject *)self;
+    if (alias->parameters == NULL) {
+        alias->parameters = _Py_make_parameters(alias->args);
+        if (alias->parameters == NULL) {
+            return NULL;
+        }
+    }
+    return Py_NewRef(alias->parameters);
+}
+
+static PyObject *
+ga_unpacked_tuple_args(PyObject *self, void *unused)
+{
+    gaobject *alias = (gaobject *)self;
+    if (alias->starred && alias->origin == (PyObject *)&PyTuple_Type) {
+        return Py_NewRef(alias->args);
+    }
+    Py_RETURN_NONE;
+}
+
+static PyGetSetDef ga_properties[] = {
+    {"__parameters__", ga_parameters, (setter)NULL, PyDoc_STR("Type variables in the GenericAlias."), NULL},
+    {"__typing_unpacked_tuple_args__", ga_unpacked_tuple_args, (setter)NULL, NULL},
+    {0}
+};
+
+/* A helper function to create GenericAlias' args tuple and set its attributes.
+ * Returns 1 on success, 0 on failure.
+ */
+static inline int
+setup_ga(gaobject *alias, PyObject *origin, PyObject *args) {
+    if (!PyTuple_Check(args)) {
+        args = PyTuple_Pack(1, args);
+        if (args == NULL) {
+            return 0;
+        }
+    }
+    else {
+        Py_INCREF(args);
+    }
+
+    alias->origin = Py_NewRef(origin);
+    alias->args = args;
+    alias->parameters = NULL;
+    alias->weakreflist = NULL;
+
+    if (PyVectorcall_Function(origin) != NULL) {
+        alias->vectorcall = ga_vectorcall;
+    }
+    else {
+        alias->vectorcall = NULL;
+    }
+
+    return 1;
+}
+
+static PyObject *
+ga_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+    if (!_PyArg_NoKeywords("GenericAlias", kwds)) {
+        return NULL;
+    }
+    if (!_PyArg_CheckPositional("GenericAlias", PyTuple_GET_SIZE(args), 2, 2)) {
+        return NULL;
+    }
+    PyObject *origin = PyTuple_GET_ITEM(args, 0);
+    PyObject *arguments = PyTuple_GET_ITEM(args, 1);
+    gaobject *self = (gaobject *)type->tp_alloc(type, 0);
+    if (self == NULL) {
+        return NULL;
+    }
+    if (!setup_ga(self, origin, arguments)) {
+        Py_DECREF(self);
+        return NULL;
+    }
+    return (PyObject *)self;
+}
+
+static PyNumberMethods ga_as_number = {
+        .nb_or = _Py_union_type_or, // Add __or__ function
+};
+
+static PyObject *
+ga_iternext(gaiterobject *gi) {
+    if (gi->obj == NULL) {
+        PyErr_SetNone(PyExc_StopIteration);
+        return NULL;
+    }
+    gaobject *alias = (gaobject *)gi->obj;
+    PyObject *starred_alias = Py_GenericAlias(alias->origin, alias->args);
+    if (starred_alias == NULL) {
+        return NULL;
+    }
+    ((gaobject *)starred_alias)->starred = true;
+    Py_SETREF(gi->obj, NULL);
+    return starred_alias;
+}
+
+static void
+ga_iter_dealloc(gaiterobject *gi) {
+    PyObject_GC_UnTrack(gi);
+    Py_XDECREF(gi->obj);
+    PyObject_GC_Del(gi);
+}
+
+static int
+ga_iter_traverse(gaiterobject *gi, visitproc visit, void *arg)
+{
+    Py_VISIT(gi->obj);
+    return 0;
+}
+
+static int
+ga_iter_clear(PyObject *self) {
+    gaiterobject *gi = (gaiterobject *)self;
+    Py_CLEAR(gi->obj);
+    return 0;
+}
+
+static PyObject *
+ga_iter_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    PyObject *iter = _PyEval_GetBuiltin(&_Py_ID(iter));
+    gaiterobject *gi = (gaiterobject *)self;
+
+    /* _PyEval_GetBuiltin can invoke arbitrary code,
+     * call must be before access of iterator pointers.
+     * see issue #101765 */
+
+    if (gi->obj)
+        return Py_BuildValue("N(O)", iter, gi->obj);
+    else
+        return Py_BuildValue("N(())", iter);
+}
+
+static PyMethodDef ga_iter_methods[] = {
+    {"__reduce__", ga_iter_reduce, METH_NOARGS},
+    {0}
+};
+
+// gh-91632: _Py_GenericAliasIterType is exported  to be cleared
+// in _PyTypes_FiniTypes.
+PyTypeObject _Py_GenericAliasIterType = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    .tp_name = "generic_alias_iterator",
+    .tp_basicsize = sizeof(gaiterobject),
+    .tp_iter = PyObject_SelfIter,
+    .tp_iternext = (iternextfunc)ga_iternext,
+    .tp_traverse = (traverseproc)ga_iter_traverse,
+    .tp_methods = ga_iter_methods,
+    .tp_dealloc = (destructor)ga_iter_dealloc,
+    .tp_clear = (inquiry)ga_iter_clear,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+};
+
+static PyObject *
+ga_iter(PyObject *self) {
+    gaiterobject *gi = PyObject_GC_New(gaiterobject, &_Py_GenericAliasIterType);
+    if (gi == NULL) {
+        return NULL;
+    }
+    gi->obj = Py_NewRef(self);
+    PyObject_GC_Track(gi);
+    return (PyObject *)gi;
+}
+
+// TODO:
+// - argument clinic?
+// - cache?
+PyTypeObject Py_GenericAliasType = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    .tp_name = "types.GenericAlias",
+    .tp_doc = genericalias__doc__,
+    .tp_basicsize = sizeof(gaobject),
+    .tp_dealloc = ga_dealloc,
+    .tp_repr = ga_repr,
+    .tp_as_number = &ga_as_number,  // allow X | Y of GenericAlias objs
+    .tp_as_mapping = &ga_as_mapping,
+    .tp_hash = ga_hash,
+    .tp_call = ga_call,
+    .tp_getattro = ga_getattro,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_VECTORCALL,
+    .tp_traverse = ga_traverse,
+    .tp_richcompare = ga_richcompare,
+    .tp_weaklistoffset = offsetof(gaobject, weakreflist),
+    .tp_methods = ga_methods,
+    .tp_members = ga_members,
+    .tp_alloc = PyType_GenericAlloc,
+    .tp_new = ga_new,
+    .tp_free = PyObject_GC_Del,
+    .tp_getset = ga_properties,
+    .tp_iter = (getiterfunc)ga_iter,
+    .tp_vectorcall_offset = offsetof(gaobject, vectorcall),
+};
+
+PyObject *
+Py_GenericAlias(PyObject *origin, PyObject *args)
+{
+    gaobject *alias = (gaobject*) PyType_GenericAlloc(
+            (PyTypeObject *)&Py_GenericAliasType, 0);
+    if (alias == NULL) {
+        return NULL;
+    }
+    if (!setup_ga(alias, origin, args)) {
+        Py_DECREF(alias);
+        return NULL;
+    }
+    return (PyObject *)alias;
+}

From 66908658103d448de251d3073e8341b21ed0c77c Mon Sep 17 00:00:00 2001
From: Prakash Sellathurai <prakashsellathurai@gmail.com>
Date: Sat, 18 Apr 2026 18:44:13 +0530
Subject: [PATCH 2/3] Revert "[3.13]  gh-148222: Fix NULL dereference bugs in
 genericaliasobject.c (#148226)"

This reverts commit 83552a67e60a422234db564942f5053ab1576ed4.
---
 ...-04-07-20-37-23.gh-issue-148222.uF4D4E.rst |    1 -
 Objects/genericaliasobject.c                  | 2073 +++++++++--------
 2 files changed, 1037 insertions(+), 1037 deletions(-)
 delete mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst
deleted file mode 100644
index 2c273fc4daba3d..00000000000000
--- a/Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst
+++ /dev/null
@@ -1 +0,0 @@
-Fix vectorcall support in :class:`types.GenericAlias` when the underlying type does not support the vectorcall protocol. Fix possible leaks in :class:`types.GenericAlias` and :class:`types.UnionType` in case of memory error.
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 3af8f349074eec..8e59b3884cf529 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -1,1036 +1,1037 @@
-// types.GenericAlias -- used to represent e.g. list[int].
-
-#include "Python.h"
-#include "pycore_ceval.h"         // _PyEval_GetBuiltin()
-#include "pycore_modsupport.h"    // _PyArg_NoKeywords()
-#include "pycore_object.h"
-#include "pycore_unionobject.h"   // _Py_union_type_or, _PyGenericAlias_Check
-#include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
-
-
-#include <stdbool.h>
-
-typedef struct {
-    PyObject_HEAD
-    PyObject *origin;
-    PyObject *args;
-    PyObject *parameters;
-    PyObject *weakreflist;
-    // Whether we're a starred type, e.g. *tuple[int].
-    bool starred;
-    vectorcallfunc vectorcall;
-} gaobject;
-
-typedef struct {
-    PyObject_HEAD
-    PyObject *obj;  /* Set to NULL when iterator is exhausted */
-} gaiterobject;
-
-static void
-ga_dealloc(PyObject *self)
-{
-    gaobject *alias = (gaobject *)self;
-
-    _PyObject_GC_UNTRACK(self);
-    FT_CLEAR_WEAKREFS((PyObject *)alias, alias->weakreflist);
-    Py_XDECREF(alias->origin);
-    Py_XDECREF(alias->args);
-    Py_XDECREF(alias->parameters);
-    Py_TYPE(self)->tp_free(self);
-}
-
-static int
-ga_traverse(PyObject *self, visitproc visit, void *arg)
-{
-    gaobject *alias = (gaobject *)self;
-    Py_VISIT(alias->origin);
-    Py_VISIT(alias->args);
-    Py_VISIT(alias->parameters);
-    return 0;
-}
-
-static int
-ga_repr_item(_PyUnicodeWriter *writer, PyObject *p)
-{
-    PyObject *qualname = NULL;
-    PyObject *module = NULL;
-    PyObject *r = NULL;
-    int rc;
-
-    if (p == Py_Ellipsis) {
-        // The Ellipsis object
-        r = PyUnicode_FromString("...");
-        goto done;
-    }
-
-    if ((rc = PyObject_HasAttrWithError(p, &_Py_ID(__origin__))) > 0 &&
-        (rc = PyObject_HasAttrWithError(p, &_Py_ID(__args__))) > 0)
-    {
-        // It looks like a GenericAlias
-        goto use_repr;
-    }
-    if (rc < 0) {
-        goto done;
-    }
-
-    if (PyObject_GetOptionalAttr(p, &_Py_ID(__qualname__), &qualname) < 0) {
-        goto done;
-    }
-    if (qualname == NULL) {
-        goto use_repr;
-    }
-    if (PyObject_GetOptionalAttr(p, &_Py_ID(__module__), &module) < 0) {
-        goto done;
-    }
-    if (module == NULL || module == Py_None) {
-        goto use_repr;
-    }
-
-    // Looks like a class
-    if (PyUnicode_Check(module) &&
-        _PyUnicode_EqualToASCIIString(module, "builtins"))
-    {
-        // builtins don't need a module name
-        r = PyObject_Str(qualname);
-        goto done;
-    }
-    else {
-        r = PyUnicode_FromFormat("%S.%S", module, qualname);
-        goto done;
-    }
-
-use_repr:
-    r = PyObject_Repr(p);
-
-done:
-    Py_XDECREF(qualname);
-    Py_XDECREF(module);
-    if (r == NULL) {
-        // error if any of the above PyObject_Repr/PyUnicode_From* fail
-        rc = -1;
-    }
-    else {
-        rc = _PyUnicodeWriter_WriteStr(writer, r);
-        Py_DECREF(r);
-    }
-    return rc;
-}
-
-static int
-ga_repr_items_list(_PyUnicodeWriter *writer, PyObject *p)
-{
-    assert(PyList_CheckExact(p));
-
-    Py_ssize_t len = PyList_GET_SIZE(p);
-
-    if (_PyUnicodeWriter_WriteASCIIString(writer, "[", 1) < 0) {
-        return -1;
-    }
-
-    for (Py_ssize_t i = 0; i < len; i++) {
-        if (i > 0) {
-            if (_PyUnicodeWriter_WriteASCIIString(writer, ", ", 2) < 0) {
-                return -1;
-            }
-        }
-        PyObject *item = PyList_GetItemRef(p, i);
-        if (item == NULL) {
-            return -1;  // list can be mutated in a callback
-        }
-        if (ga_repr_item(writer, item) < 0) {
-            Py_DECREF(item);
-            return -1;
-        }
-        Py_DECREF(item);
-    }
-
-    if (_PyUnicodeWriter_WriteASCIIString(writer, "]", 1) < 0) {
-        return -1;
-    }
-
-    return 0;
-}
-
-static PyObject *
-ga_repr(PyObject *self)
-{
-    gaobject *alias = (gaobject *)self;
-    Py_ssize_t len = PyTuple_GET_SIZE(alias->args);
-
-    _PyUnicodeWriter writer;
-    _PyUnicodeWriter_Init(&writer);
-
-    if (alias->starred) {
-        if (_PyUnicodeWriter_WriteASCIIString(&writer, "*", 1) < 0) {
-            goto error;
-        }
-    }
-    if (ga_repr_item(&writer, alias->origin) < 0) {
-        goto error;
-    }
-    if (_PyUnicodeWriter_WriteASCIIString(&writer, "[", 1) < 0) {
-        goto error;
-    }
-    for (Py_ssize_t i = 0; i < len; i++) {
-        if (i > 0) {
-            if (_PyUnicodeWriter_WriteASCIIString(&writer, ", ", 2) < 0) {
-                goto error;
-            }
-        }
-        PyObject *p = PyTuple_GET_ITEM(alias->args, i);
-        if (PyList_CheckExact(p)) {
-            // Looks like we are working with ParamSpec's list of type args:
-            if (ga_repr_items_list(&writer, p) < 0) {
-                goto error;
-            }
-        }
-        else if (ga_repr_item(&writer, p) < 0) {
-            goto error;
-        }
-    }
-    if (len == 0) {
-        // for something like tuple[()] we should print a "()"
-        if (_PyUnicodeWriter_WriteASCIIString(&writer, "()", 2) < 0) {
-            goto error;
-        }
-    }
-    if (_PyUnicodeWriter_WriteASCIIString(&writer, "]", 1) < 0) {
-        goto error;
-    }
-    return _PyUnicodeWriter_Finish(&writer);
-error:
-    _PyUnicodeWriter_Dealloc(&writer);
-    return NULL;
-}
-
-// Index of item in self[:len], or -1 if not found (self is a tuple)
-static Py_ssize_t
-tuple_index(PyObject *self, Py_ssize_t len, PyObject *item)
-{
-    for (Py_ssize_t i = 0; i < len; i++) {
-        if (PyTuple_GET_ITEM(self, i) == item) {
-            return i;
-        }
-    }
-    return -1;
-}
-
-static int
-tuple_add(PyObject *self, Py_ssize_t len, PyObject *item)
-{
-    if (tuple_index(self, len, item) < 0) {
-        PyTuple_SET_ITEM(self, len, Py_NewRef(item));
-        return 1;
-    }
-    return 0;
-}
-
-static Py_ssize_t
-tuple_extend(PyObject **dst, Py_ssize_t dstindex,
-             PyObject **src, Py_ssize_t count)
-{
-    assert(count >= 0);
-    if (_PyTuple_Resize(dst, PyTuple_GET_SIZE(*dst) + count - 1) != 0) {
-        return -1;
-    }
-    assert(dstindex + count <= PyTuple_GET_SIZE(*dst));
-    for (Py_ssize_t i = 0; i < count; ++i) {
-        PyObject *item = src[i];
-        PyTuple_SET_ITEM(*dst, dstindex + i, Py_NewRef(item));
-    }
-    return dstindex + count;
-}
-
-PyObject *
-_Py_make_parameters(PyObject *args)
-{
-    Py_ssize_t nargs = PyTuple_GET_SIZE(args);
-    Py_ssize_t len = nargs;
-    PyObject *parameters = PyTuple_New(len);
-    if (parameters == NULL)
-        return NULL;
-    Py_ssize_t iparam = 0;
-    for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
-        PyObject *t = PyTuple_GET_ITEM(args, iarg);
-        // We don't want __parameters__ descriptor of a bare Python class.
-        if (PyType_Check(t)) {
-            continue;
-        }
-        int rc = PyObject_HasAttrWithError(t, &_Py_ID(__typing_subst__));
-        if (rc < 0) {
-            Py_DECREF(parameters);
-            return NULL;
-        }
-        if (rc) {
-            iparam += tuple_add(parameters, iparam, t);
-        }
-        else {
-            PyObject *subparams;
-            if (PyObject_GetOptionalAttr(t, &_Py_ID(__parameters__),
-                                     &subparams) < 0) {
-                Py_DECREF(parameters);
-                return NULL;
-            }
-            if (subparams && PyTuple_Check(subparams)) {
-                Py_ssize_t len2 = PyTuple_GET_SIZE(subparams);
-                Py_ssize_t needed = len2 - 1 - (iarg - iparam);
-                if (needed > 0) {
-                    len += needed;
-                    if (_PyTuple_Resize(&parameters, len) < 0) {
-                        Py_DECREF(subparams);
-                        return NULL;
-                    }
-                }
-                for (Py_ssize_t j = 0; j < len2; j++) {
-                    PyObject *t2 = PyTuple_GET_ITEM(subparams, j);
-                    iparam += tuple_add(parameters, iparam, t2);
-                }
-            }
-            Py_XDECREF(subparams);
-        }
-    }
-    if (iparam < len) {
-        if (_PyTuple_Resize(&parameters, iparam) < 0) {
-            Py_XDECREF(parameters);
-            return NULL;
-        }
-    }
-    return parameters;
-}
-
-/* If obj is a generic alias, substitute type variables params
-   with substitutions argitems.  For example, if obj is list[T],
-   params is (T, S), and argitems is (str, int), return list[str].
-   If obj doesn't have a __parameters__ attribute or that's not
-   a non-empty tuple, return a new reference to obj. */
-static PyObject *
-subs_tvars(PyObject *obj, PyObject *params,
-           PyObject **argitems, Py_ssize_t nargs)
-{
-    PyObject *subparams;
-    if (PyObject_GetOptionalAttr(obj, &_Py_ID(__parameters__), &subparams) < 0) {
-        return NULL;
-    }
-    if (subparams && PyTuple_Check(subparams) && PyTuple_GET_SIZE(subparams)) {
-        Py_ssize_t nparams = PyTuple_GET_SIZE(params);
-        Py_ssize_t nsubargs = PyTuple_GET_SIZE(subparams);
-        PyObject *subargs = PyTuple_New(nsubargs);
-        if (subargs == NULL) {
-            Py_DECREF(subparams);
-            return NULL;
-        }
-        Py_ssize_t j = 0;
-        for (Py_ssize_t i = 0; i < nsubargs; ++i) {
-            PyObject *arg = PyTuple_GET_ITEM(subparams, i);
-            Py_ssize_t iparam = tuple_index(params, nparams, arg);
-            if (iparam >= 0) {
-                PyObject *param = PyTuple_GET_ITEM(params, iparam);
-                arg = argitems[iparam];
-                if (Py_TYPE(param)->tp_iter && PyTuple_Check(arg)) {  // TypeVarTuple
-                    j = tuple_extend(&subargs, j,
-                                    &PyTuple_GET_ITEM(arg, 0),
-                                    PyTuple_GET_SIZE(arg));
-                    if (j < 0) {
-                        return NULL;
-                    }
-                    continue;
-                }
-            }
-            PyTuple_SET_ITEM(subargs, j, Py_NewRef(arg));
-            j++;
-        }
-        assert(j == PyTuple_GET_SIZE(subargs));
-
-        obj = PyObject_GetItem(obj, subargs);
-
-        Py_DECREF(subargs);
-    }
-    else {
-        Py_INCREF(obj);
-    }
-    Py_XDECREF(subparams);
-    return obj;
-}
-
-static int
-_is_unpacked_typevartuple(PyObject *arg)
-{
-    PyObject *tmp;
-    if (PyType_Check(arg)) { // TODO: Add test
-        return 0;
-    }
-    int res = PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_is_unpacked_typevartuple__), &tmp);
-    if (res > 0) {
-        res = PyObject_IsTrue(tmp);
-        Py_DECREF(tmp);
-    }
-    return res;
-}
-
-static PyObject *
-_unpacked_tuple_args(PyObject *arg)
-{
-    PyObject *result;
-    assert(!PyType_Check(arg));
-    // Fast path
-    if (_PyGenericAlias_Check(arg) &&
-            ((gaobject *)arg)->starred &&
-            ((gaobject *)arg)->origin == (PyObject *)&PyTuple_Type)
-    {
-        result = ((gaobject *)arg)->args;
-        return Py_NewRef(result);
-    }
-
-    if (PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_unpacked_tuple_args__), &result) > 0) {
-        if (result == Py_None) {
-            Py_DECREF(result);
-            return NULL;
-        }
-        return result;
-    }
-    return NULL;
-}
-
-static PyObject *
-_unpack_args(PyObject *item)
-{
-    PyObject *newargs = PyList_New(0);
-    if (newargs == NULL) {
-        return NULL;
-    }
-    int is_tuple = PyTuple_Check(item);
-    Py_ssize_t nitems = is_tuple ? PyTuple_GET_SIZE(item) : 1;
-    PyObject **argitems = is_tuple ? &PyTuple_GET_ITEM(item, 0) : &item;
-    for (Py_ssize_t i = 0; i < nitems; i++) {
-        item = argitems[i];
-        if (!PyType_Check(item)) {
-            PyObject *subargs = _unpacked_tuple_args(item);
-            if (subargs != NULL &&
-                PyTuple_Check(subargs) &&
-                !(PyTuple_GET_SIZE(subargs) &&
-                  PyTuple_GET_ITEM(subargs, PyTuple_GET_SIZE(subargs)-1) == Py_Ellipsis))
-            {
-                if (PyList_SetSlice(newargs, PY_SSIZE_T_MAX, PY_SSIZE_T_MAX, subargs) < 0) {
-                    Py_DECREF(subargs);
-                    Py_DECREF(newargs);
-                    return NULL;
-                }
-                Py_DECREF(subargs);
-                continue;
-            }
-            Py_XDECREF(subargs);
-            if (PyErr_Occurred()) {
-                Py_DECREF(newargs);
-                return NULL;
-            }
-        }
-        if (PyList_Append(newargs, item) < 0) {
-            Py_DECREF(newargs);
-            return NULL;
-        }
-    }
-    Py_SETREF(newargs, PySequence_Tuple(newargs));
-    return newargs;
-}
-
-PyObject *
-_Py_subs_parameters(PyObject *self, PyObject *args, PyObject *parameters, PyObject *item)
-{
-    Py_ssize_t nparams = PyTuple_GET_SIZE(parameters);
-    if (nparams == 0) {
-        return PyErr_Format(PyExc_TypeError,
-                            "%R is not a generic class",
-                            self);
-    }
-    item = _unpack_args(item);
-    for (Py_ssize_t i = 0; i < nparams; i++) {
-        PyObject *param = PyTuple_GET_ITEM(parameters, i);
-        PyObject *prepare, *tmp;
-        if (PyObject_GetOptionalAttr(param, &_Py_ID(__typing_prepare_subst__), &prepare) < 0) {
-            Py_DECREF(item);
-            return NULL;
-        }
-        if (prepare && prepare != Py_None) {
-            if (PyTuple_Check(item)) {
-                tmp = PyObject_CallFunction(prepare, "OO", self, item);
-            }
-            else {
-                tmp = PyObject_CallFunction(prepare, "O(O)", self, item);
-            }
-            Py_DECREF(prepare);
-            Py_SETREF(item, tmp);
-            if (item == NULL) {
-                return NULL;
-            }
-        }
-    }
-    int is_tuple = PyTuple_Check(item);
-    Py_ssize_t nitems = is_tuple ? PyTuple_GET_SIZE(item) : 1;
-    PyObject **argitems = is_tuple ? &PyTuple_GET_ITEM(item, 0) : &item;
-    if (nitems != nparams) {
-        Py_DECREF(item);
-        return PyErr_Format(PyExc_TypeError,
-                            "Too %s arguments for %R; actual %zd, expected %zd",
-                            nitems > nparams ? "many" : "few",
-                            self, nitems, nparams);
-    }
-    /* Replace all type variables (specified by parameters)
-       with corresponding values specified by argitems.
-        t = list[T];          t[int]      -> newargs = [int]
-        t = dict[str, T];     t[int]      -> newargs = [str, int]
-        t = dict[T, list[S]]; t[str, int] -> newargs = [str, list[int]]
-     */
-    Py_ssize_t nargs = PyTuple_GET_SIZE(args);
-    PyObject *newargs = PyTuple_New(nargs);
-    if (newargs == NULL) {
-        Py_DECREF(item);
-        return NULL;
-    }
-    for (Py_ssize_t iarg = 0, jarg = 0; iarg < nargs; iarg++) {
-        PyObject *arg = PyTuple_GET_ITEM(args, iarg);
-        if (PyType_Check(arg)) {
-            PyTuple_SET_ITEM(newargs, jarg, Py_NewRef(arg));
-            jarg++;
-            continue;
-        }
-
-        int unpack = _is_unpacked_typevartuple(arg);
-        if (unpack < 0) {
-            Py_DECREF(newargs);
-            Py_DECREF(item);
-            return NULL;
-        }
-        PyObject *subst;
-        if (PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_subst__), &subst) < 0) {
-            Py_DECREF(newargs);
-            Py_DECREF(item);
-            return NULL;
-        }
-        if (subst) {
-            Py_ssize_t iparam = tuple_index(parameters, nparams, arg);
-            assert(iparam >= 0);
-            arg = PyObject_CallOneArg(subst, argitems[iparam]);
-            Py_DECREF(subst);
-        }
-        else {
-            arg = subs_tvars(arg, parameters, argitems, nitems);
-        }
-        if (arg == NULL) {
-            Py_DECREF(newargs);
-            Py_DECREF(item);
-            return NULL;
-        }
-        if (unpack) {
-            if (!PyTuple_Check(arg)) {
-                Py_DECREF(newargs);
-                Py_DECREF(item);
-                PyObject *original = PyTuple_GET_ITEM(args, iarg);
-                PyErr_Format(PyExc_TypeError,
-                             "expected __typing_subst__ of %T objects to return a tuple, not %T",
-                             original, arg);
-                Py_DECREF(arg);
-                return NULL;
-            }
-            jarg = tuple_extend(&newargs, jarg,
-                    &PyTuple_GET_ITEM(arg, 0), PyTuple_GET_SIZE(arg));
-            Py_DECREF(arg);
-            if (jarg < 0) {
-                Py_DECREF(item);
-                assert(newargs == NULL);
-                return NULL;
-            }
-        }
-        else {
-            PyTuple_SET_ITEM(newargs, jarg, arg);
-            jarg++;
-        }
-    }
-
-    Py_DECREF(item);
-    return newargs;
-}
-
-PyDoc_STRVAR(genericalias__doc__,
-"GenericAlias(origin, args, /)\n"
-"--\n\n"
-"Represent a PEP 585 generic type\n"
-"\n"
-"E.g. for t = list[int], t.__origin__ is list and t.__args__ is (int,).");
-
-static PyObject *
-ga_getitem(PyObject *self, PyObject *item)
-{
-    gaobject *alias = (gaobject *)self;
-    // Populate __parameters__ if needed.
-    if (alias->parameters == NULL) {
-        alias->parameters = _Py_make_parameters(alias->args);
-        if (alias->parameters == NULL) {
-            return NULL;
-        }
-    }
-
-    PyObject *newargs = _Py_subs_parameters(self, alias->args, alias->parameters, item);
-    if (newargs == NULL) {
-        return NULL;
-    }
-
-    PyObject *res = Py_GenericAlias(alias->origin, newargs);
-    if (res == NULL) {
-        Py_DECREF(newargs);
-        return NULL;
-    }
-    ((gaobject *)res)->starred = alias->starred;
-
-    Py_DECREF(newargs);
-    return res;
-}
-
-static PyMappingMethods ga_as_mapping = {
-    .mp_subscript = ga_getitem,
-};
-
-static Py_hash_t
-ga_hash(PyObject *self)
-{
-    gaobject *alias = (gaobject *)self;
-    // TODO: Hash in the hash for the origin
-    Py_hash_t h0 = PyObject_Hash(alias->origin);
-    if (h0 == -1) {
-        return -1;
-    }
-    Py_hash_t h1 = PyObject_Hash(alias->args);
-    if (h1 == -1) {
-        return -1;
-    }
-    return h0 ^ h1;
-}
-
-static inline PyObject *
-set_orig_class(PyObject *obj, PyObject *self)
-{
-    if (obj != NULL) {
-        if (PyObject_SetAttr(obj, &_Py_ID(__orig_class__), self) < 0) {
-            if (!PyErr_ExceptionMatches(PyExc_AttributeError) &&
-                !PyErr_ExceptionMatches(PyExc_TypeError))
-            {
-                Py_DECREF(obj);
-                return NULL;
-            }
-            PyErr_Clear();
-        }
-    }
-    return obj;
-}
-
-static PyObject *
-ga_call(PyObject *self, PyObject *args, PyObject *kwds)
-{
-    gaobject *alias = (gaobject *)self;
-    PyObject *obj = PyObject_Call(alias->origin, args, kwds);
-    return set_orig_class(obj, self);
-}
-
-static PyObject *
-ga_vectorcall(PyObject *self, PyObject *const *args,
-              size_t nargsf, PyObject *kwnames)
-{
-    gaobject *alias = (gaobject *) self;
-    PyObject *obj = PyObject_Vectorcall(alias->origin, args, nargsf, kwnames);
-    return set_orig_class(obj, self);
-}
-
-static const char* const attr_exceptions[] = {
-    "__class__",
-    "__origin__",
-    "__args__",
-    "__unpacked__",
-    "__parameters__",
-    "__typing_unpacked_tuple_args__",
-    "__mro_entries__",
-    "__reduce_ex__",  // needed so we don't look up object.__reduce_ex__
-    "__reduce__",
-    NULL,
-};
-
-static const char* const attr_blocked[] = {
-    "__bases__",
-    "__copy__",
-    "__deepcopy__",
-    NULL,
-};
-
-static PyObject *
-ga_getattro(PyObject *self, PyObject *name)
-{
-    gaobject *alias = (gaobject *)self;
-    if (PyUnicode_Check(name)) {
-        // When we check blocked attrs, we don't allow to proxy them to `__origin__`.
-        // Otherwise, we can break existing code.
-        for (const char * const *p = attr_blocked; ; p++) {
-            if (*p == NULL) {
-                break;
-            }
-            if (_PyUnicode_EqualToASCIIString(name, *p)) {
-                goto generic_getattr;
-            }
-        }
-
-        // When we see own attrs, it has a priority over `__origin__`'s attr.
-        for (const char * const *p = attr_exceptions; ; p++) {
-            if (*p == NULL) {
-                return PyObject_GetAttr(alias->origin, name);
-            }
-            if (_PyUnicode_EqualToASCIIString(name, *p)) {
-                goto generic_getattr;
-            }
-        }
-    }
-
-generic_getattr:
-    return PyObject_GenericGetAttr(self, name);
-}
-
-static PyObject *
-ga_richcompare(PyObject *a, PyObject *b, int op)
-{
-    if (!_PyGenericAlias_Check(b) ||
-        (op != Py_EQ && op != Py_NE))
-    {
-        Py_RETURN_NOTIMPLEMENTED;
-    }
-
-    if (op == Py_NE) {
-        PyObject *eq = ga_richcompare(a, b, Py_EQ);
-        if (eq == NULL)
-            return NULL;
-        Py_DECREF(eq);
-        if (eq == Py_True) {
-            Py_RETURN_FALSE;
-        }
-        else {
-            Py_RETURN_TRUE;
-        }
-    }
-
-    gaobject *aa = (gaobject *)a;
-    gaobject *bb = (gaobject *)b;
-    if (aa->starred != bb->starred) {
-        Py_RETURN_FALSE;
-    }
-    int eq = PyObject_RichCompareBool(aa->origin, bb->origin, Py_EQ);
-    if (eq < 0) {
-        return NULL;
-    }
-    if (!eq) {
-        Py_RETURN_FALSE;
-    }
-    return PyObject_RichCompare(aa->args, bb->args, Py_EQ);
-}
-
-static PyObject *
-ga_mro_entries(PyObject *self, PyObject *args)
-{
-    gaobject *alias = (gaobject *)self;
-    return PyTuple_Pack(1, alias->origin);
-}
-
-static PyObject *
-ga_instancecheck(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    PyErr_SetString(PyExc_TypeError,
-                    "isinstance() argument 2 cannot be a parameterized generic");
-    return NULL;
-}
-
-static PyObject *
-ga_subclasscheck(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    PyErr_SetString(PyExc_TypeError,
-                    "issubclass() argument 2 cannot be a parameterized generic");
-    return NULL;
-}
-
-static PyObject *
-ga_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    gaobject *alias = (gaobject *)self;
-    if (alias->starred) {
-        PyObject *tmp = Py_GenericAlias(alias->origin, alias->args);
-        if (tmp != NULL) {
-            Py_SETREF(tmp, PyObject_GetIter(tmp));
-        }
-        if (tmp == NULL) {
-            return NULL;
-        }
-        return Py_BuildValue("N(N)", _PyEval_GetBuiltin(&_Py_ID(next)), tmp);
-    }
-    return Py_BuildValue("O(OO)", Py_TYPE(alias),
-                         alias->origin, alias->args);
-}
-
-static PyObject *
-ga_dir(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    gaobject *alias = (gaobject *)self;
-    PyObject *dir = PyObject_Dir(alias->origin);
-    if (dir == NULL) {
-        return NULL;
-    }
-
-    PyObject *dir_entry = NULL;
-    for (const char * const *p = attr_exceptions; ; p++) {
-        if (*p == NULL) {
-            break;
-        }
-        else {
-            dir_entry = PyUnicode_FromString(*p);
-            if (dir_entry == NULL) {
-                goto error;
-            }
-            int contains = PySequence_Contains(dir, dir_entry);
-            if (contains < 0) {
-                goto error;
-            }
-            if (contains == 0 && PyList_Append(dir, dir_entry) < 0) {
-                goto error;
-            }
-
-            Py_CLEAR(dir_entry);
-        }
-    }
-    return dir;
-
-error:
-    Py_DECREF(dir);
-    Py_XDECREF(dir_entry);
-    return NULL;
-}
-
-static PyMethodDef ga_methods[] = {
-    {"__mro_entries__", ga_mro_entries, METH_O},
-    {"__instancecheck__", ga_instancecheck, METH_O},
-    {"__subclasscheck__", ga_subclasscheck, METH_O},
-    {"__reduce__", ga_reduce, METH_NOARGS},
-    {"__dir__", ga_dir, METH_NOARGS},
-    {0}
-};
-
-static PyMemberDef ga_members[] = {
-    {"__origin__", _Py_T_OBJECT, offsetof(gaobject, origin), Py_READONLY},
-    {"__args__", _Py_T_OBJECT, offsetof(gaobject, args), Py_READONLY},
-    {"__unpacked__", Py_T_BOOL, offsetof(gaobject, starred), Py_READONLY},
-    {0}
-};
-
-static PyObject *
-ga_parameters(PyObject *self, void *unused)
-{
-    gaobject *alias = (gaobject *)self;
-    if (alias->parameters == NULL) {
-        alias->parameters = _Py_make_parameters(alias->args);
-        if (alias->parameters == NULL) {
-            return NULL;
-        }
-    }
-    return Py_NewRef(alias->parameters);
-}
-
-static PyObject *
-ga_unpacked_tuple_args(PyObject *self, void *unused)
-{
-    gaobject *alias = (gaobject *)self;
-    if (alias->starred && alias->origin == (PyObject *)&PyTuple_Type) {
-        return Py_NewRef(alias->args);
-    }
-    Py_RETURN_NONE;
-}
-
-static PyGetSetDef ga_properties[] = {
-    {"__parameters__", ga_parameters, (setter)NULL, PyDoc_STR("Type variables in the GenericAlias."), NULL},
-    {"__typing_unpacked_tuple_args__", ga_unpacked_tuple_args, (setter)NULL, NULL},
-    {0}
-};
-
-/* A helper function to create GenericAlias' args tuple and set its attributes.
- * Returns 1 on success, 0 on failure.
- */
-static inline int
-setup_ga(gaobject *alias, PyObject *origin, PyObject *args) {
-    if (!PyTuple_Check(args)) {
-        args = PyTuple_Pack(1, args);
-        if (args == NULL) {
-            return 0;
-        }
-    }
-    else {
-        Py_INCREF(args);
-    }
-
-    alias->origin = Py_NewRef(origin);
-    alias->args = args;
-    alias->parameters = NULL;
-    alias->weakreflist = NULL;
-
-    if (PyVectorcall_Function(origin) != NULL) {
-        alias->vectorcall = ga_vectorcall;
-    }
-    else {
-        alias->vectorcall = NULL;
-    }
-
-    return 1;
-}
-
-static PyObject *
-ga_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
-{
-    if (!_PyArg_NoKeywords("GenericAlias", kwds)) {
-        return NULL;
-    }
-    if (!_PyArg_CheckPositional("GenericAlias", PyTuple_GET_SIZE(args), 2, 2)) {
-        return NULL;
-    }
-    PyObject *origin = PyTuple_GET_ITEM(args, 0);
-    PyObject *arguments = PyTuple_GET_ITEM(args, 1);
-    gaobject *self = (gaobject *)type->tp_alloc(type, 0);
-    if (self == NULL) {
-        return NULL;
-    }
-    if (!setup_ga(self, origin, arguments)) {
-        Py_DECREF(self);
-        return NULL;
-    }
-    return (PyObject *)self;
-}
-
-static PyNumberMethods ga_as_number = {
-        .nb_or = _Py_union_type_or, // Add __or__ function
-};
-
-static PyObject *
-ga_iternext(gaiterobject *gi) {
-    if (gi->obj == NULL) {
-        PyErr_SetNone(PyExc_StopIteration);
-        return NULL;
-    }
-    gaobject *alias = (gaobject *)gi->obj;
-    PyObject *starred_alias = Py_GenericAlias(alias->origin, alias->args);
-    if (starred_alias == NULL) {
-        return NULL;
-    }
-    ((gaobject *)starred_alias)->starred = true;
-    Py_SETREF(gi->obj, NULL);
-    return starred_alias;
-}
-
-static void
-ga_iter_dealloc(gaiterobject *gi) {
-    PyObject_GC_UnTrack(gi);
-    Py_XDECREF(gi->obj);
-    PyObject_GC_Del(gi);
-}
-
-static int
-ga_iter_traverse(gaiterobject *gi, visitproc visit, void *arg)
-{
-    Py_VISIT(gi->obj);
-    return 0;
-}
-
-static int
-ga_iter_clear(PyObject *self) {
-    gaiterobject *gi = (gaiterobject *)self;
-    Py_CLEAR(gi->obj);
-    return 0;
-}
-
-static PyObject *
-ga_iter_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
-{
-    PyObject *iter = _PyEval_GetBuiltin(&_Py_ID(iter));
-    gaiterobject *gi = (gaiterobject *)self;
-
-    /* _PyEval_GetBuiltin can invoke arbitrary code,
-     * call must be before access of iterator pointers.
-     * see issue #101765 */
-
-    if (gi->obj)
-        return Py_BuildValue("N(O)", iter, gi->obj);
-    else
-        return Py_BuildValue("N(())", iter);
-}
-
-static PyMethodDef ga_iter_methods[] = {
-    {"__reduce__", ga_iter_reduce, METH_NOARGS},
-    {0}
-};
-
-// gh-91632: _Py_GenericAliasIterType is exported  to be cleared
-// in _PyTypes_FiniTypes.
-PyTypeObject _Py_GenericAliasIterType = {
-    PyVarObject_HEAD_INIT(&PyType_Type, 0)
-    .tp_name = "generic_alias_iterator",
-    .tp_basicsize = sizeof(gaiterobject),
-    .tp_iter = PyObject_SelfIter,
-    .tp_iternext = (iternextfunc)ga_iternext,
-    .tp_traverse = (traverseproc)ga_iter_traverse,
-    .tp_methods = ga_iter_methods,
-    .tp_dealloc = (destructor)ga_iter_dealloc,
-    .tp_clear = (inquiry)ga_iter_clear,
-    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
-};
-
-static PyObject *
-ga_iter(PyObject *self) {
-    gaiterobject *gi = PyObject_GC_New(gaiterobject, &_Py_GenericAliasIterType);
-    if (gi == NULL) {
-        return NULL;
-    }
-    gi->obj = Py_NewRef(self);
-    PyObject_GC_Track(gi);
-    return (PyObject *)gi;
-}
-
-// TODO:
-// - argument clinic?
-// - cache?
-PyTypeObject Py_GenericAliasType = {
-    PyVarObject_HEAD_INIT(&PyType_Type, 0)
-    .tp_name = "types.GenericAlias",
-    .tp_doc = genericalias__doc__,
-    .tp_basicsize = sizeof(gaobject),
-    .tp_dealloc = ga_dealloc,
-    .tp_repr = ga_repr,
-    .tp_as_number = &ga_as_number,  // allow X | Y of GenericAlias objs
-    .tp_as_mapping = &ga_as_mapping,
-    .tp_hash = ga_hash,
-    .tp_call = ga_call,
-    .tp_getattro = ga_getattro,
-    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_VECTORCALL,
-    .tp_traverse = ga_traverse,
-    .tp_richcompare = ga_richcompare,
-    .tp_weaklistoffset = offsetof(gaobject, weakreflist),
-    .tp_methods = ga_methods,
-    .tp_members = ga_members,
-    .tp_alloc = PyType_GenericAlloc,
-    .tp_new = ga_new,
-    .tp_free = PyObject_GC_Del,
-    .tp_getset = ga_properties,
-    .tp_iter = (getiterfunc)ga_iter,
-    .tp_vectorcall_offset = offsetof(gaobject, vectorcall),
-};
-
-PyObject *
-Py_GenericAlias(PyObject *origin, PyObject *args)
-{
-    gaobject *alias = (gaobject*) PyType_GenericAlloc(
-            (PyTypeObject *)&Py_GenericAliasType, 0);
-    if (alias == NULL) {
-        return NULL;
-    }
-    if (!setup_ga(alias, origin, args)) {
-        Py_DECREF(alias);
-        return NULL;
-    }
-    return (PyObject *)alias;
-}
+// types.GenericAlias -- used to represent e.g. list[int].
+
+#include "Python.h"
+#include "pycore_ceval.h"         // _PyEval_GetBuiltin()
+#include "pycore_modsupport.h"    // _PyArg_NoKeywords()
+#include "pycore_object.h"
+#include "pycore_unionobject.h"   // _Py_union_type_or, _PyGenericAlias_Check
+#include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
+
+
+#include <stdbool.h>
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *origin;
+    PyObject *args;
+    PyObject *parameters;
+    PyObject *weakreflist;
+    // Whether we're a starred type, e.g. *tuple[int].
+    bool starred;
+    vectorcallfunc vectorcall;
+} gaobject;
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *obj;  /* Set to NULL when iterator is exhausted */
+} gaiterobject;
+
+static void
+ga_dealloc(PyObject *self)
+{
+    gaobject *alias = (gaobject *)self;
+
+    _PyObject_GC_UNTRACK(self);
+    FT_CLEAR_WEAKREFS((PyObject *)alias, alias->weakreflist);
+    Py_XDECREF(alias->origin);
+    Py_XDECREF(alias->args);
+    Py_XDECREF(alias->parameters);
+    Py_TYPE(self)->tp_free(self);
+}
+
+static int
+ga_traverse(PyObject *self, visitproc visit, void *arg)
+{
+    gaobject *alias = (gaobject *)self;
+    Py_VISIT(alias->origin);
+    Py_VISIT(alias->args);
+    Py_VISIT(alias->parameters);
+    return 0;
+}
+
+static int
+ga_repr_item(_PyUnicodeWriter *writer, PyObject *p)
+{
+    PyObject *qualname = NULL;
+    PyObject *module = NULL;
+    PyObject *r = NULL;
+    int rc;
+
+    if (p == Py_Ellipsis) {
+        // The Ellipsis object
+        r = PyUnicode_FromString("...");
+        goto done;
+    }
+
+    if ((rc = PyObject_HasAttrWithError(p, &_Py_ID(__origin__))) > 0 &&
+        (rc = PyObject_HasAttrWithError(p, &_Py_ID(__args__))) > 0)
+    {
+        // It looks like a GenericAlias
+        goto use_repr;
+    }
+    if (rc < 0) {
+        goto done;
+    }
+
+    if (PyObject_GetOptionalAttr(p, &_Py_ID(__qualname__), &qualname) < 0) {
+        goto done;
+    }
+    if (qualname == NULL) {
+        goto use_repr;
+    }
+    if (PyObject_GetOptionalAttr(p, &_Py_ID(__module__), &module) < 0) {
+        goto done;
+    }
+    if (module == NULL || module == Py_None) {
+        goto use_repr;
+    }
+
+    // Looks like a class
+    if (PyUnicode_Check(module) &&
+        _PyUnicode_EqualToASCIIString(module, "builtins"))
+    {
+        // builtins don't need a module name
+        r = PyObject_Str(qualname);
+        goto done;
+    }
+    else {
+        r = PyUnicode_FromFormat("%S.%S", module, qualname);
+        goto done;
+    }
+
+use_repr:
+    r = PyObject_Repr(p);
+
+done:
+    Py_XDECREF(qualname);
+    Py_XDECREF(module);
+    if (r == NULL) {
+        // error if any of the above PyObject_Repr/PyUnicode_From* fail
+        rc = -1;
+    }
+    else {
+        rc = _PyUnicodeWriter_WriteStr(writer, r);
+        Py_DECREF(r);
+    }
+    return rc;
+}
+
+static int
+ga_repr_items_list(_PyUnicodeWriter *writer, PyObject *p)
+{
+    assert(PyList_CheckExact(p));
+
+    Py_ssize_t len = PyList_GET_SIZE(p);
+
+    if (_PyUnicodeWriter_WriteASCIIString(writer, "[", 1) < 0) {
+        return -1;
+    }
+
+    for (Py_ssize_t i = 0; i < len; i++) {
+        if (i > 0) {
+            if (_PyUnicodeWriter_WriteASCIIString(writer, ", ", 2) < 0) {
+                return -1;
+            }
+        }
+        PyObject *item = PyList_GetItemRef(p, i);
+        if (item == NULL) {
+            return -1;  // list can be mutated in a callback
+        }
+        if (ga_repr_item(writer, item) < 0) {
+            Py_DECREF(item);
+            return -1;
+        }
+        Py_DECREF(item);
+    }
+
+    if (_PyUnicodeWriter_WriteASCIIString(writer, "]", 1) < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static PyObject *
+ga_repr(PyObject *self)
+{
+    gaobject *alias = (gaobject *)self;
+    Py_ssize_t len = PyTuple_GET_SIZE(alias->args);
+
+    _PyUnicodeWriter writer;
+    _PyUnicodeWriter_Init(&writer);
+
+    if (alias->starred) {
+        if (_PyUnicodeWriter_WriteASCIIString(&writer, "*", 1) < 0) {
+            goto error;
+        }
+    }
+    if (ga_repr_item(&writer, alias->origin) < 0) {
+        goto error;
+    }
+    if (_PyUnicodeWriter_WriteASCIIString(&writer, "[", 1) < 0) {
+        goto error;
+    }
+    for (Py_ssize_t i = 0; i < len; i++) {
+        if (i > 0) {
+            if (_PyUnicodeWriter_WriteASCIIString(&writer, ", ", 2) < 0) {
+                goto error;
+            }
+        }
+        PyObject *p = PyTuple_GET_ITEM(alias->args, i);
+        if (PyList_CheckExact(p)) {
+            // Looks like we are working with ParamSpec's list of type args:
+            if (ga_repr_items_list(&writer, p) < 0) {
+                goto error;
+            }
+        }
+        else if (ga_repr_item(&writer, p) < 0) {
+            goto error;
+        }
+    }
+    if (len == 0) {
+        // for something like tuple[()] we should print a "()"
+        if (_PyUnicodeWriter_WriteASCIIString(&writer, "()", 2) < 0) {
+            goto error;
+        }
+    }
+    if (_PyUnicodeWriter_WriteASCIIString(&writer, "]", 1) < 0) {
+        goto error;
+    }
+    return _PyUnicodeWriter_Finish(&writer);
+error:
+    _PyUnicodeWriter_Dealloc(&writer);
+    return NULL;
+}
+
+// Index of item in self[:len], or -1 if not found (self is a tuple)
+static Py_ssize_t
+tuple_index(PyObject *self, Py_ssize_t len, PyObject *item)
+{
+    for (Py_ssize_t i = 0; i < len; i++) {
+        if (PyTuple_GET_ITEM(self, i) == item) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+static int
+tuple_add(PyObject *self, Py_ssize_t len, PyObject *item)
+{
+    if (tuple_index(self, len, item) < 0) {
+        PyTuple_SET_ITEM(self, len, Py_NewRef(item));
+        return 1;
+    }
+    return 0;
+}
+
+static Py_ssize_t
+tuple_extend(PyObject **dst, Py_ssize_t dstindex,
+             PyObject **src, Py_ssize_t count)
+{
+    assert(count >= 0);
+    if (_PyTuple_Resize(dst, PyTuple_GET_SIZE(*dst) + count - 1) != 0) {
+        return -1;
+    }
+    assert(dstindex + count <= PyTuple_GET_SIZE(*dst));
+    for (Py_ssize_t i = 0; i < count; ++i) {
+        PyObject *item = src[i];
+        PyTuple_SET_ITEM(*dst, dstindex + i, Py_NewRef(item));
+    }
+    return dstindex + count;
+}
+
+PyObject *
+_Py_make_parameters(PyObject *args)
+{
+    Py_ssize_t nargs = PyTuple_GET_SIZE(args);
+    Py_ssize_t len = nargs;
+    PyObject *parameters = PyTuple_New(len);
+    if (parameters == NULL)
+        return NULL;
+    Py_ssize_t iparam = 0;
+    for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
+        PyObject *t = PyTuple_GET_ITEM(args, iarg);
+        // We don't want __parameters__ descriptor of a bare Python class.
+        if (PyType_Check(t)) {
+            continue;
+        }
+        int rc = PyObject_HasAttrWithError(t, &_Py_ID(__typing_subst__));
+        if (rc < 0) {
+            Py_DECREF(parameters);
+            return NULL;
+        }
+        if (rc) {
+            iparam += tuple_add(parameters, iparam, t);
+        }
+        else {
+            PyObject *subparams;
+            if (PyObject_GetOptionalAttr(t, &_Py_ID(__parameters__),
+                                     &subparams) < 0) {
+                Py_DECREF(parameters);
+                return NULL;
+            }
+            if (subparams && PyTuple_Check(subparams)) {
+                Py_ssize_t len2 = PyTuple_GET_SIZE(subparams);
+                Py_ssize_t needed = len2 - 1 - (iarg - iparam);
+                if (needed > 0) {
+                    len += needed;
+                    if (_PyTuple_Resize(&parameters, len) < 0) {
+                        Py_DECREF(subparams);
+                        Py_DECREF(parameters);
+                        return NULL;
+                    }
+                }
+                for (Py_ssize_t j = 0; j < len2; j++) {
+                    PyObject *t2 = PyTuple_GET_ITEM(subparams, j);
+                    iparam += tuple_add(parameters, iparam, t2);
+                }
+            }
+            Py_XDECREF(subparams);
+        }
+    }
+    if (iparam < len) {
+        if (_PyTuple_Resize(&parameters, iparam) < 0) {
+            Py_XDECREF(parameters);
+            return NULL;
+        }
+    }
+    return parameters;
+}
+
+/* If obj is a generic alias, substitute type variables params
+   with substitutions argitems.  For example, if obj is list[T],
+   params is (T, S), and argitems is (str, int), return list[str].
+   If obj doesn't have a __parameters__ attribute or that's not
+   a non-empty tuple, return a new reference to obj. */
+static PyObject *
+subs_tvars(PyObject *obj, PyObject *params,
+           PyObject **argitems, Py_ssize_t nargs)
+{
+    PyObject *subparams;
+    if (PyObject_GetOptionalAttr(obj, &_Py_ID(__parameters__), &subparams) < 0) {
+        return NULL;
+    }
+    if (subparams && PyTuple_Check(subparams) && PyTuple_GET_SIZE(subparams)) {
+        Py_ssize_t nparams = PyTuple_GET_SIZE(params);
+        Py_ssize_t nsubargs = PyTuple_GET_SIZE(subparams);
+        PyObject *subargs = PyTuple_New(nsubargs);
+        if (subargs == NULL) {
+            Py_DECREF(subparams);
+            return NULL;
+        }
+        Py_ssize_t j = 0;
+        for (Py_ssize_t i = 0; i < nsubargs; ++i) {
+            PyObject *arg = PyTuple_GET_ITEM(subparams, i);
+            Py_ssize_t iparam = tuple_index(params, nparams, arg);
+            if (iparam >= 0) {
+                PyObject *param = PyTuple_GET_ITEM(params, iparam);
+                arg = argitems[iparam];
+                if (Py_TYPE(param)->tp_iter && PyTuple_Check(arg)) {  // TypeVarTuple
+                    j = tuple_extend(&subargs, j,
+                                    &PyTuple_GET_ITEM(arg, 0),
+                                    PyTuple_GET_SIZE(arg));
+                    if (j < 0) {
+                        return NULL;
+                    }
+                    continue;
+                }
+            }
+            PyTuple_SET_ITEM(subargs, j, Py_NewRef(arg));
+            j++;
+        }
+        assert(j == PyTuple_GET_SIZE(subargs));
+
+        obj = PyObject_GetItem(obj, subargs);
+
+        Py_DECREF(subargs);
+    }
+    else {
+        Py_INCREF(obj);
+    }
+    Py_XDECREF(subparams);
+    return obj;
+}
+
+static int
+_is_unpacked_typevartuple(PyObject *arg)
+{
+    PyObject *tmp;
+    if (PyType_Check(arg)) { // TODO: Add test
+        return 0;
+    }
+    int res = PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_is_unpacked_typevartuple__), &tmp);
+    if (res > 0) {
+        res = PyObject_IsTrue(tmp);
+        Py_DECREF(tmp);
+    }
+    return res;
+}
+
+static PyObject *
+_unpacked_tuple_args(PyObject *arg)
+{
+    PyObject *result;
+    assert(!PyType_Check(arg));
+    // Fast path
+    if (_PyGenericAlias_Check(arg) &&
+            ((gaobject *)arg)->starred &&
+            ((gaobject *)arg)->origin == (PyObject *)&PyTuple_Type)
+    {
+        result = ((gaobject *)arg)->args;
+        return Py_NewRef(result);
+    }
+
+    if (PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_unpacked_tuple_args__), &result) > 0) {
+        if (result == Py_None) {
+            Py_DECREF(result);
+            return NULL;
+        }
+        return result;
+    }
+    return NULL;
+}
+
+static PyObject *
+_unpack_args(PyObject *item)
+{
+    PyObject *newargs = PyList_New(0);
+    if (newargs == NULL) {
+        return NULL;
+    }
+    int is_tuple = PyTuple_Check(item);
+    Py_ssize_t nitems = is_tuple ? PyTuple_GET_SIZE(item) : 1;
+    PyObject **argitems = is_tuple ? &PyTuple_GET_ITEM(item, 0) : &item;
+    for (Py_ssize_t i = 0; i < nitems; i++) {
+        item = argitems[i];
+        if (!PyType_Check(item)) {
+            PyObject *subargs = _unpacked_tuple_args(item);
+            if (subargs != NULL &&
+                PyTuple_Check(subargs) &&
+                !(PyTuple_GET_SIZE(subargs) &&
+                  PyTuple_GET_ITEM(subargs, PyTuple_GET_SIZE(subargs)-1) == Py_Ellipsis))
+            {
+                if (PyList_SetSlice(newargs, PY_SSIZE_T_MAX, PY_SSIZE_T_MAX, subargs) < 0) {
+                    Py_DECREF(subargs);
+                    Py_DECREF(newargs);
+                    return NULL;
+                }
+                Py_DECREF(subargs);
+                continue;
+            }
+            Py_XDECREF(subargs);
+            if (PyErr_Occurred()) {
+                Py_DECREF(newargs);
+                return NULL;
+            }
+        }
+        if (PyList_Append(newargs, item) < 0) {
+            Py_DECREF(newargs);
+            return NULL;
+        }
+    }
+    Py_SETREF(newargs, PySequence_Tuple(newargs));
+    return newargs;
+}
+
+PyObject *
+_Py_subs_parameters(PyObject *self, PyObject *args, PyObject *parameters, PyObject *item)
+{
+    Py_ssize_t nparams = PyTuple_GET_SIZE(parameters);
+    if (nparams == 0) {
+        return PyErr_Format(PyExc_TypeError,
+                            "%R is not a generic class",
+                            self);
+    }
+    item = _unpack_args(item);
+    for (Py_ssize_t i = 0; i < nparams; i++) {
+        PyObject *param = PyTuple_GET_ITEM(parameters, i);
+        PyObject *prepare, *tmp;
+        if (PyObject_GetOptionalAttr(param, &_Py_ID(__typing_prepare_subst__), &prepare) < 0) {
+            Py_DECREF(item);
+            return NULL;
+        }
+        if (prepare && prepare != Py_None) {
+            if (PyTuple_Check(item)) {
+                tmp = PyObject_CallFunction(prepare, "OO", self, item);
+            }
+            else {
+                tmp = PyObject_CallFunction(prepare, "O(O)", self, item);
+            }
+            Py_DECREF(prepare);
+            Py_SETREF(item, tmp);
+            if (item == NULL) {
+                return NULL;
+            }
+        }
+    }
+    int is_tuple = PyTuple_Check(item);
+    Py_ssize_t nitems = is_tuple ? PyTuple_GET_SIZE(item) : 1;
+    PyObject **argitems = is_tuple ? &PyTuple_GET_ITEM(item, 0) : &item;
+    if (nitems != nparams) {
+        Py_DECREF(item);
+        return PyErr_Format(PyExc_TypeError,
+                            "Too %s arguments for %R; actual %zd, expected %zd",
+                            nitems > nparams ? "many" : "few",
+                            self, nitems, nparams);
+    }
+    /* Replace all type variables (specified by parameters)
+       with corresponding values specified by argitems.
+        t = list[T];          t[int]      -> newargs = [int]
+        t = dict[str, T];     t[int]      -> newargs = [str, int]
+        t = dict[T, list[S]]; t[str, int] -> newargs = [str, list[int]]
+     */
+    Py_ssize_t nargs = PyTuple_GET_SIZE(args);
+    PyObject *newargs = PyTuple_New(nargs);
+    if (newargs == NULL) {
+        Py_DECREF(item);
+        return NULL;
+    }
+    for (Py_ssize_t iarg = 0, jarg = 0; iarg < nargs; iarg++) {
+        PyObject *arg = PyTuple_GET_ITEM(args, iarg);
+        if (PyType_Check(arg)) {
+            PyTuple_SET_ITEM(newargs, jarg, Py_NewRef(arg));
+            jarg++;
+            continue;
+        }
+
+        int unpack = _is_unpacked_typevartuple(arg);
+        if (unpack < 0) {
+            Py_DECREF(newargs);
+            Py_DECREF(item);
+            return NULL;
+        }
+        PyObject *subst;
+        if (PyObject_GetOptionalAttr(arg, &_Py_ID(__typing_subst__), &subst) < 0) {
+            Py_DECREF(newargs);
+            Py_DECREF(item);
+            return NULL;
+        }
+        if (subst) {
+            Py_ssize_t iparam = tuple_index(parameters, nparams, arg);
+            assert(iparam >= 0);
+            arg = PyObject_CallOneArg(subst, argitems[iparam]);
+            Py_DECREF(subst);
+        }
+        else {
+            arg = subs_tvars(arg, parameters, argitems, nitems);
+        }
+        if (arg == NULL) {
+            Py_DECREF(newargs);
+            Py_DECREF(item);
+            return NULL;
+        }
+        if (unpack) {
+            if (!PyTuple_Check(arg)) {
+                Py_DECREF(newargs);
+                Py_DECREF(item);
+                PyObject *original = PyTuple_GET_ITEM(args, iarg);
+                PyErr_Format(PyExc_TypeError,
+                             "expected __typing_subst__ of %T objects to return a tuple, not %T",
+                             original, arg);
+                Py_DECREF(arg);
+                return NULL;
+            }
+            jarg = tuple_extend(&newargs, jarg,
+                    &PyTuple_GET_ITEM(arg, 0), PyTuple_GET_SIZE(arg));
+            Py_DECREF(arg);
+            if (jarg < 0) {
+                Py_DECREF(item);
+                assert(newargs == NULL);
+                return NULL;
+            }
+        }
+        else {
+            PyTuple_SET_ITEM(newargs, jarg, arg);
+            jarg++;
+        }
+    }
+
+    Py_DECREF(item);
+    return newargs;
+}
+
+PyDoc_STRVAR(genericalias__doc__,
+"GenericAlias(origin, args, /)\n"
+"--\n\n"
+"Represent a PEP 585 generic type\n"
+"\n"
+"E.g. for t = list[int], t.__origin__ is list and t.__args__ is (int,).");
+
+static PyObject *
+ga_getitem(PyObject *self, PyObject *item)
+{
+    gaobject *alias = (gaobject *)self;
+    // Populate __parameters__ if needed.
+    if (alias->parameters == NULL) {
+        alias->parameters = _Py_make_parameters(alias->args);
+        if (alias->parameters == NULL) {
+            return NULL;
+        }
+    }
+
+    PyObject *newargs = _Py_subs_parameters(self, alias->args, alias->parameters, item);
+    if (newargs == NULL) {
+        return NULL;
+    }
+
+    PyObject *res = Py_GenericAlias(alias->origin, newargs);
+    if (res == NULL) {
+        Py_DECREF(newargs);
+        return NULL;
+    }
+    ((gaobject *)res)->starred = alias->starred;
+
+    Py_DECREF(newargs);
+    return res;
+}
+
+static PyMappingMethods ga_as_mapping = {
+    .mp_subscript = ga_getitem,
+};
+
+static Py_hash_t
+ga_hash(PyObject *self)
+{
+    gaobject *alias = (gaobject *)self;
+    // TODO: Hash in the hash for the origin
+    Py_hash_t h0 = PyObject_Hash(alias->origin);
+    if (h0 == -1) {
+        return -1;
+    }
+    Py_hash_t h1 = PyObject_Hash(alias->args);
+    if (h1 == -1) {
+        return -1;
+    }
+    return h0 ^ h1;
+}
+
+static inline PyObject *
+set_orig_class(PyObject *obj, PyObject *self)
+{
+    if (obj != NULL) {
+        if (PyObject_SetAttr(obj, &_Py_ID(__orig_class__), self) < 0) {
+            if (!PyErr_ExceptionMatches(PyExc_AttributeError) &&
+                !PyErr_ExceptionMatches(PyExc_TypeError))
+            {
+                Py_DECREF(obj);
+                return NULL;
+            }
+            PyErr_Clear();
+        }
+    }
+    return obj;
+}
+
+static PyObject *
+ga_call(PyObject *self, PyObject *args, PyObject *kwds)
+{
+    gaobject *alias = (gaobject *)self;
+    PyObject *obj = PyObject_Call(alias->origin, args, kwds);
+    return set_orig_class(obj, self);
+}
+
+static PyObject *
+ga_vectorcall(PyObject *self, PyObject *const *args,
+              size_t nargsf, PyObject *kwnames)
+{
+    gaobject *alias = (gaobject *) self;
+    PyObject *obj = PyVectorcall_Function(alias->origin)(alias->origin, args, nargsf, kwnames);
+    return set_orig_class(obj, self);
+}
+
+static const char* const attr_exceptions[] = {
+    "__class__",
+    "__origin__",
+    "__args__",
+    "__unpacked__",
+    "__parameters__",
+    "__typing_unpacked_tuple_args__",
+    "__mro_entries__",
+    "__reduce_ex__",  // needed so we don't look up object.__reduce_ex__
+    "__reduce__",
+    NULL,
+};
+
+static const char* const attr_blocked[] = {
+    "__bases__",
+    "__copy__",
+    "__deepcopy__",
+    NULL,
+};
+
+static PyObject *
+ga_getattro(PyObject *self, PyObject *name)
+{
+    gaobject *alias = (gaobject *)self;
+    if (PyUnicode_Check(name)) {
+        // When we check blocked attrs, we don't allow to proxy them to `__origin__`.
+        // Otherwise, we can break existing code.
+        for (const char * const *p = attr_blocked; ; p++) {
+            if (*p == NULL) {
+                break;
+            }
+            if (_PyUnicode_EqualToASCIIString(name, *p)) {
+                goto generic_getattr;
+            }
+        }
+
+        // When we see own attrs, it has a priority over `__origin__`'s attr.
+        for (const char * const *p = attr_exceptions; ; p++) {
+            if (*p == NULL) {
+                return PyObject_GetAttr(alias->origin, name);
+            }
+            if (_PyUnicode_EqualToASCIIString(name, *p)) {
+                goto generic_getattr;
+            }
+        }
+    }
+
+generic_getattr:
+    return PyObject_GenericGetAttr(self, name);
+}
+
+static PyObject *
+ga_richcompare(PyObject *a, PyObject *b, int op)
+{
+    if (!_PyGenericAlias_Check(b) ||
+        (op != Py_EQ && op != Py_NE))
+    {
+        Py_RETURN_NOTIMPLEMENTED;
+    }
+
+    if (op == Py_NE) {
+        PyObject *eq = ga_richcompare(a, b, Py_EQ);
+        if (eq == NULL)
+            return NULL;
+        Py_DECREF(eq);
+        if (eq == Py_True) {
+            Py_RETURN_FALSE;
+        }
+        else {
+            Py_RETURN_TRUE;
+        }
+    }
+
+    gaobject *aa = (gaobject *)a;
+    gaobject *bb = (gaobject *)b;
+    if (aa->starred != bb->starred) {
+        Py_RETURN_FALSE;
+    }
+    int eq = PyObject_RichCompareBool(aa->origin, bb->origin, Py_EQ);
+    if (eq < 0) {
+        return NULL;
+    }
+    if (!eq) {
+        Py_RETURN_FALSE;
+    }
+    return PyObject_RichCompare(aa->args, bb->args, Py_EQ);
+}
+
+static PyObject *
+ga_mro_entries(PyObject *self, PyObject *args)
+{
+    gaobject *alias = (gaobject *)self;
+    return PyTuple_Pack(1, alias->origin);
+}
+
+static PyObject *
+ga_instancecheck(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    PyErr_SetString(PyExc_TypeError,
+                    "isinstance() argument 2 cannot be a parameterized generic");
+    return NULL;
+}
+
+static PyObject *
+ga_subclasscheck(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    PyErr_SetString(PyExc_TypeError,
+                    "issubclass() argument 2 cannot be a parameterized generic");
+    return NULL;
+}
+
+static PyObject *
+ga_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    gaobject *alias = (gaobject *)self;
+    if (alias->starred) {
+        PyObject *tmp = Py_GenericAlias(alias->origin, alias->args);
+        if (tmp != NULL) {
+            Py_SETREF(tmp, PyObject_GetIter(tmp));
+        }
+        if (tmp == NULL) {
+            return NULL;
+        }
+        return Py_BuildValue("N(N)", _PyEval_GetBuiltin(&_Py_ID(next)), tmp);
+    }
+    return Py_BuildValue("O(OO)", Py_TYPE(alias),
+                         alias->origin, alias->args);
+}
+
+static PyObject *
+ga_dir(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    gaobject *alias = (gaobject *)self;
+    PyObject *dir = PyObject_Dir(alias->origin);
+    if (dir == NULL) {
+        return NULL;
+    }
+
+    PyObject *dir_entry = NULL;
+    for (const char * const *p = attr_exceptions; ; p++) {
+        if (*p == NULL) {
+            break;
+        }
+        else {
+            dir_entry = PyUnicode_FromString(*p);
+            if (dir_entry == NULL) {
+                goto error;
+            }
+            int contains = PySequence_Contains(dir, dir_entry);
+            if (contains < 0) {
+                goto error;
+            }
+            if (contains == 0 && PyList_Append(dir, dir_entry) < 0) {
+                goto error;
+            }
+
+            Py_CLEAR(dir_entry);
+        }
+    }
+    return dir;
+
+error:
+    Py_DECREF(dir);
+    Py_XDECREF(dir_entry);
+    return NULL;
+}
+
+static PyMethodDef ga_methods[] = {
+    {"__mro_entries__", ga_mro_entries, METH_O},
+    {"__instancecheck__", ga_instancecheck, METH_O},
+    {"__subclasscheck__", ga_subclasscheck, METH_O},
+    {"__reduce__", ga_reduce, METH_NOARGS},
+    {"__dir__", ga_dir, METH_NOARGS},
+    {0}
+};
+
+static PyMemberDef ga_members[] = {
+    {"__origin__", _Py_T_OBJECT, offsetof(gaobject, origin), Py_READONLY},
+    {"__args__", _Py_T_OBJECT, offsetof(gaobject, args), Py_READONLY},
+    {"__unpacked__", Py_T_BOOL, offsetof(gaobject, starred), Py_READONLY},
+    {0}
+};
+
+static PyObject *
+ga_parameters(PyObject *self, void *unused)
+{
+    gaobject *alias = (gaobject *)self;
+    if (alias->parameters == NULL) {
+        alias->parameters = _Py_make_parameters(alias->args);
+        if (alias->parameters == NULL) {
+            return NULL;
+        }
+    }
+    return Py_NewRef(alias->parameters);
+}
+
+static PyObject *
+ga_unpacked_tuple_args(PyObject *self, void *unused)
+{
+    gaobject *alias = (gaobject *)self;
+    if (alias->starred && alias->origin == (PyObject *)&PyTuple_Type) {
+        return Py_NewRef(alias->args);
+    }
+    Py_RETURN_NONE;
+}
+
+static PyGetSetDef ga_properties[] = {
+    {"__parameters__", ga_parameters, (setter)NULL, PyDoc_STR("Type variables in the GenericAlias."), NULL},
+    {"__typing_unpacked_tuple_args__", ga_unpacked_tuple_args, (setter)NULL, NULL},
+    {0}
+};
+
+/* A helper function to create GenericAlias' args tuple and set its attributes.
+ * Returns 1 on success, 0 on failure.
+ */
+static inline int
+setup_ga(gaobject *alias, PyObject *origin, PyObject *args) {
+    if (!PyTuple_Check(args)) {
+        args = PyTuple_Pack(1, args);
+        if (args == NULL) {
+            return 0;
+        }
+    }
+    else {
+        Py_INCREF(args);
+    }
+
+    alias->origin = Py_NewRef(origin);
+    alias->args = args;
+    alias->parameters = NULL;
+    alias->weakreflist = NULL;
+
+    if (PyVectorcall_Function(origin) != NULL) {
+        alias->vectorcall = ga_vectorcall;
+    }
+    else {
+        alias->vectorcall = NULL;
+    }
+
+    return 1;
+}
+
+static PyObject *
+ga_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+    if (!_PyArg_NoKeywords("GenericAlias", kwds)) {
+        return NULL;
+    }
+    if (!_PyArg_CheckPositional("GenericAlias", PyTuple_GET_SIZE(args), 2, 2)) {
+        return NULL;
+    }
+    PyObject *origin = PyTuple_GET_ITEM(args, 0);
+    PyObject *arguments = PyTuple_GET_ITEM(args, 1);
+    gaobject *self = (gaobject *)type->tp_alloc(type, 0);
+    if (self == NULL) {
+        return NULL;
+    }
+    if (!setup_ga(self, origin, arguments)) {
+        Py_DECREF(self);
+        return NULL;
+    }
+    return (PyObject *)self;
+}
+
+static PyNumberMethods ga_as_number = {
+        .nb_or = _Py_union_type_or, // Add __or__ function
+};
+
+static PyObject *
+ga_iternext(gaiterobject *gi) {
+    if (gi->obj == NULL) {
+        PyErr_SetNone(PyExc_StopIteration);
+        return NULL;
+    }
+    gaobject *alias = (gaobject *)gi->obj;
+    PyObject *starred_alias = Py_GenericAlias(alias->origin, alias->args);
+    if (starred_alias == NULL) {
+        return NULL;
+    }
+    ((gaobject *)starred_alias)->starred = true;
+    Py_SETREF(gi->obj, NULL);
+    return starred_alias;
+}
+
+static void
+ga_iter_dealloc(gaiterobject *gi) {
+    PyObject_GC_UnTrack(gi);
+    Py_XDECREF(gi->obj);
+    PyObject_GC_Del(gi);
+}
+
+static int
+ga_iter_traverse(gaiterobject *gi, visitproc visit, void *arg)
+{
+    Py_VISIT(gi->obj);
+    return 0;
+}
+
+static int
+ga_iter_clear(PyObject *self) {
+    gaiterobject *gi = (gaiterobject *)self;
+    Py_CLEAR(gi->obj);
+    return 0;
+}
+
+static PyObject *
+ga_iter_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    PyObject *iter = _PyEval_GetBuiltin(&_Py_ID(iter));
+    gaiterobject *gi = (gaiterobject *)self;
+
+    /* _PyEval_GetBuiltin can invoke arbitrary code,
+     * call must be before access of iterator pointers.
+     * see issue #101765 */
+
+    if (gi->obj)
+        return Py_BuildValue("N(O)", iter, gi->obj);
+    else
+        return Py_BuildValue("N(())", iter);
+}
+
+static PyMethodDef ga_iter_methods[] = {
+    {"__reduce__", ga_iter_reduce, METH_NOARGS},
+    {0}
+};
+
+// gh-91632: _Py_GenericAliasIterType is exported  to be cleared
+// in _PyTypes_FiniTypes.
+PyTypeObject _Py_GenericAliasIterType = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    .tp_name = "generic_alias_iterator",
+    .tp_basicsize = sizeof(gaiterobject),
+    .tp_iter = PyObject_SelfIter,
+    .tp_iternext = (iternextfunc)ga_iternext,
+    .tp_traverse = (traverseproc)ga_iter_traverse,
+    .tp_methods = ga_iter_methods,
+    .tp_dealloc = (destructor)ga_iter_dealloc,
+    .tp_clear = (inquiry)ga_iter_clear,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+};
+
+static PyObject *
+ga_iter(PyObject *self) {
+    gaiterobject *gi = PyObject_GC_New(gaiterobject, &_Py_GenericAliasIterType);
+    if (gi == NULL) {
+        return NULL;
+    }
+    gi->obj = Py_NewRef(self);
+    PyObject_GC_Track(gi);
+    return (PyObject *)gi;
+}
+
+// TODO:
+// - argument clinic?
+// - cache?
+PyTypeObject Py_GenericAliasType = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    .tp_name = "types.GenericAlias",
+    .tp_doc = genericalias__doc__,
+    .tp_basicsize = sizeof(gaobject),
+    .tp_dealloc = ga_dealloc,
+    .tp_repr = ga_repr,
+    .tp_as_number = &ga_as_number,  // allow X | Y of GenericAlias objs
+    .tp_as_mapping = &ga_as_mapping,
+    .tp_hash = ga_hash,
+    .tp_call = ga_call,
+    .tp_getattro = ga_getattro,
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_VECTORCALL,
+    .tp_traverse = ga_traverse,
+    .tp_richcompare = ga_richcompare,
+    .tp_weaklistoffset = offsetof(gaobject, weakreflist),
+    .tp_methods = ga_methods,
+    .tp_members = ga_members,
+    .tp_alloc = PyType_GenericAlloc,
+    .tp_new = ga_new,
+    .tp_free = PyObject_GC_Del,
+    .tp_getset = ga_properties,
+    .tp_iter = (getiterfunc)ga_iter,
+    .tp_vectorcall_offset = offsetof(gaobject, vectorcall),
+};
+
+PyObject *
+Py_GenericAlias(PyObject *origin, PyObject *args)
+{
+    gaobject *alias = (gaobject*) PyType_GenericAlloc(
+            (PyTypeObject *)&Py_GenericAliasType, 0);
+    if (alias == NULL) {
+        return NULL;
+    }
+    if (!setup_ga(alias, origin, args)) {
+        Py_DECREF(alias);
+        return NULL;
+    }
+    return (PyObject *)alias;
+}

From 7aca63fa469d54ccae48759dd5388ab0926ec84f Mon Sep 17 00:00:00 2001
From: Prakash Sellathurai <prakashsellathurai@gmail.com>
Date: Sat, 18 Apr 2026 18:54:24 +0530
Subject: [PATCH 3/3] [3.13] gh-148222: Fix NULL dereference bugs in
 genericaliasobject.c (#148226)

(cherry picked from commit 634568d030f18183212c01bd4544aa7f97e05442)
---
 .../2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst             | 1 +
 Objects/genericaliasobject.c                                   | 3 +--
 2 files changed, 2 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst
new file mode 100644
index 00000000000000..2c273fc4daba3d
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-04-07-20-37-23.gh-issue-148222.uF4D4E.rst
@@ -0,0 +1 @@
+Fix vectorcall support in :class:`types.GenericAlias` when the underlying type does not support the vectorcall protocol. Fix possible leaks in :class:`types.GenericAlias` and :class:`types.UnionType` in case of memory error.
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 8e59b3884cf529..30759ca0e0eb67 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -278,7 +278,6 @@ _Py_make_parameters(PyObject *args)
                     len += needed;
                     if (_PyTuple_Resize(&parameters, len) < 0) {
                         Py_DECREF(subparams);
-                        Py_DECREF(parameters);
                         return NULL;
                     }
                 }
@@ -636,7 +635,7 @@ ga_vectorcall(PyObject *self, PyObject *const *args,
               size_t nargsf, PyObject *kwnames)
 {
     gaobject *alias = (gaobject *) self;
-    PyObject *obj = PyVectorcall_Function(alias->origin)(alias->origin, args, nargsf, kwnames);
+    PyObject *obj = PyObject_Vectorcall(alias->origin, args, nargsf, kwnames);
     return set_orig_class(obj, self);
 }