[3.14] gh-78465: Fix error message for cls.__new__(cls, ...) where cls is not instant...

Previous error message suggested to use cls.__new__(), which
obviously does not work. Now the error message is the same as for
cls(...).
(cherry picked from commit c45f4f3ebe34529a8db3a7918e8dd2e9f7ce8e86)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index 8afc9c28182ba542cfd9223539e8eb343e1828e1..ce18518bb8aa1829fa536e64ec783961a73ea02e 100644 (file)
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -2334,6 +2334,7 @@ def check_disallow_instantiation(testcase, tp, *args, **kwds):
         qualname = f"{name}"
     msg = f"cannot create '{re.escape(qualname)}' instances"
     testcase.assertRaisesRegex(TypeError, msg, tp, *args, **kwds)
+    testcase.assertRaisesRegex(TypeError, msg, tp.__new__, tp, *args, **kwds)
 
 def get_recursion_depth():
     """Get the recursion depth of the caller function.

diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index ec9da33cf46320c3888ff8950e8fdf1d4be4f950..e2117b9588dba26b066c5050a76f2519663373d8 100644 (file)
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -869,12 +869,7 @@ class SysModuleTest(unittest.TestCase):
     def assert_raise_on_new_sys_type(self, sys_attr):
         # Users are intentionally prevented from creating new instances of
         # sys.flags, sys.version_info, and sys.getwindowsversion.
-        arg = sys_attr
-        attr_type = type(sys_attr)
-        with self.assertRaises(TypeError):
-            attr_type(arg)
-        with self.assertRaises(TypeError):
-            attr_type.__new__(attr_type, arg)
+        support.check_disallow_instantiation(self, type(sys_attr), sys_attr)
 
     def test_sys_flags_no_instantiation(self):
         self.assert_raise_on_new_sys_type(sys.flags)

diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index 02592ea5eb21a1db6d5b6d6f28fef3158e905efa..fc26e71ffcb67b4edd3bec09e94f28a47169792d 100644 (file)
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -2,7 +2,7 @@
 
 from test.support import (
     run_with_locale, cpython_only, no_rerun,
-    MISSING_C_DOCSTRINGS, EqualToForwardRef,
+    MISSING_C_DOCSTRINGS, EqualToForwardRef, check_disallow_instantiation,
 )
 from test.support.script_helper import assert_python_ok
 from test.support.import_helper import import_fresh_module
@@ -1148,8 +1148,7 @@ class UnionTests(unittest.TestCase):
                              msg='Check for union reference leak.')
 
     def test_instantiation(self):
-        with self.assertRaises(TypeError):
-            types.UnionType()
+        check_disallow_instantiation(self, types.UnionType)
         self.assertIs(int, types.UnionType[int])
         self.assertIs(int, types.UnionType[int, int])
         self.assertEqual(int | str, types.UnionType[int, str])

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-06-26-15-25-51.gh-issue-78465.MbDN8X.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-06-26-15-25-51.gh-issue-78465.MbDN8X.rst
new file mode 100644 (file)
index 0000000..99734d6
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-06-26-15-25-51.gh-issue-78465.MbDN8X.rst
@@ -0,0 +1,2 @@
+Fix error message for ``cls.__new__(cls, ...)`` where ``cls`` is not
+instantiable builtin or extension type (with ``tp_new`` set to ``NULL``).

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 32bbaecf9a3d87f42d5c7155fe5088de4ec63b24..455d32434c468833a564588e0081b1d14d7be71b 100644 (file)
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -9717,6 +9717,11 @@ tp_new_wrapper(PyObject *self, PyObject *args, PyObject *kwds)
     /* If staticbase is NULL now, it is a really weird type.
        In the spirit of backwards compatibility (?), just shut up. */
     if (staticbase && staticbase->tp_new != type->tp_new) {
+        if (staticbase->tp_new == NULL) {
+            PyErr_Format(PyExc_TypeError,
+                         "cannot create '%s' instances", subtype->tp_name);
+            return NULL;
+        }
         PyErr_Format(PyExc_TypeError,
                      "%s.__new__(%s) is not safe, use %s.__new__()",
                      type->tp_name,