Add tp_new

Include/internal/pycore_unionobject.h

@@ -16,7 +16,7 @@ extern PyObject *_Py_union_type_or(PyObject *, PyObject *);
 extern PyObject *_Py_subs_parameters(PyObject *, PyObject *, PyObject *, PyObject *);
 extern PyObject *_Py_make_parameters(PyObject *);
 extern PyObject *_Py_union_args(PyObject *self);
-extern PyObject *_Py_union_class_getitem(PyObject *cls, PyObject *args);
+extern PyObject *_Py_union_from_tuple(PyObject *args);
 
 #ifdef __cplusplus
 }

Lib/test/test_types.py

@@ -1025,6 +1025,14 @@ def test_or_type_operator_reference_cycle(self):
         self.assertLessEqual(sys.gettotalrefcount() - before, leeway,
                              msg='Check for union reference leak.')
 
+    def test_instantiation(self):
+        with self.assertRaises(TypeError):
+            types.UnionType()
+        self.assertIs(int, types.UnionType(int))
+        self.assertIs(int, types.UnionType(int, int))
+        self.assertEqual(int | str, types.UnionType(int, str))
+        self.assertEqual(int | typing.ForwardRef("str"), types.UnionType(int, "str"))
+
 
 class MappingProxyTests(unittest.TestCase):
     mappingproxy = types.MappingProxyType

Objects/typevarobject.c

@@ -2,7 +2,7 @@
 #include "Python.h"
 #include "pycore_object.h"  // _PyObject_GC_TRACK/UNTRACK
 #include "pycore_typevarobject.h"
-#include "pycore_unionobject.h"   // _Py_union_type_or, _Py_union_class_getitem
+#include "pycore_unionobject.h"   // _Py_union_type_or, _Py_union_from_tuple
 #include "structmember.h"
 
 /*[clinic input]
@@ -103,7 +103,7 @@ make_union(PyObject *self, PyObject *other)
     if (args == NULL) {
         return NULL;
     }
-    return _Py_union_class_getitem((PyObject *)&_PyUnion_Type, args);
+    return _Py_union_from_tuple(args);
 }
 
 static PyObject *

Objects/unionobject.c

@@ -387,6 +387,15 @@ _Py_union_args(PyObject *self)
     return ((unionobject *) self)->args;
 }
 
+static PyObject *
+union_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+    if (!_PyArg_NoKeywords("UnionType", kwds)) {
+        return NULL;
+    }
+    return _Py_union_from_tuple(args);
+}
+
 static PyObject *
 call_typing_func_object(const char *name, PyObject **args, size_t nargs)
 {
@@ -461,7 +470,7 @@ add_object_to_union_args(PyObject *args_list, PyObject *args_set, PyObject *obj)
 }
 
 PyObject *
-_Py_union_class_getitem(PyObject *cls, PyObject *args)
+_Py_union_from_tuple(PyObject *args)
 {
     PyObject *args_list = PyList_New(0);
     if (args_list == NULL) {
@@ -510,8 +519,14 @@ _Py_union_class_getitem(PyObject *cls, PyObject *args)
     return make_union(args_tuple);
 }
 
+static PyObject *
+union_class_getitem(PyObject *cls, PyObject *args)
+{
+    return _Py_union_from_tuple(args);
+}
+
 static PyMethodDef union_methods[] = {
-    {"__class_getitem__", _Py_union_class_getitem, METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
+    {"__class_getitem__", union_class_getitem, METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
     {0}
 };
 
@@ -531,6 +546,7 @@ PyTypeObject _PyUnion_Type = {
     .tp_getattro = union_getattro,
     .tp_members = union_members,
     .tp_methods = union_methods,
+    .tp_new = union_new,
     .tp_richcompare = union_richcompare,
     .tp_as_mapping = &union_as_mapping,
     .tp_as_number = &union_as_number,