gh-91603: Speed up isinstance/issubclass on union types

Include/internal/pycore_unionobject.h

@@ -15,6 +15,7 @@ extern PyObject *_Py_union_type_or(PyObject *, PyObject *);
 #define _PyGenericAlias_Check(op) PyObject_TypeCheck(op, &Py_GenericAliasType)
 extern PyObject *_Py_subs_parameters(PyObject *, PyObject *, PyObject *, PyObject *);
 extern PyObject *_Py_make_parameters(PyObject *);
+extern PyObject *_Py_union_args_for_check(PyObject *, bool);
 
 #ifdef __cplusplus
 }

Misc/NEWS.d/next/Core and Builtins/2022-04-17-11-03-45.gh-issue-91603.hYw1Lv.rst

@@ -0,0 +1,2 @@
+Speed-up ``isinstance`` and ``issubclass`` checks for ``types.UnionType``.
+Patch provided by Yurii Karabas.

Objects/abstract.c

@@ -2625,6 +2625,12 @@ object_recursive_isinstance(PyThreadState *tstate, PyObject *inst, PyObject *cls
         return object_isinstance(inst, cls);
     }
 
+    if (_PyUnion_Check(cls)) {
+        cls = _Py_union_args_for_check(cls, true);
+        if (!cls)
+            return -1;
+    }
+
     if (PyTuple_Check(cls)) {
         /* Not a general sequence -- that opens up the road to
            recursion and stack overflow. */
@@ -2714,6 +2720,12 @@ object_issubclass(PyThreadState *tstate, PyObject *derived, PyObject *cls)
         return recursive_issubclass(derived, cls);
     }
 
+    if (_PyUnion_Check(cls)) {
+        cls = _Py_union_args_for_check(cls, false);
+        if (!cls)
+            return -1;
+    }
+
     if (PyTuple_Check(cls)) {
 
         if (_Py_EnterRecursiveCall(tstate, " in __subclasscheck__")) {

Objects/unionobject.c

@@ -61,60 +61,6 @@ is_generic_alias_in_args(PyObject *args)
     return 1;
 }
 
-static PyObject *
-union_instancecheck(PyObject *self, PyObject *instance)
-{
-    unionobject *alias = (unionobject *) self;
-    Py_ssize_t nargs = PyTuple_GET_SIZE(alias->args);
-    if (!is_generic_alias_in_args(alias->args)) {
-        PyErr_SetString(PyExc_TypeError,
-            "isinstance() argument 2 cannot contain a parameterized generic");
-        return NULL;
-    }
-    for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
-        PyObject *arg = PyTuple_GET_ITEM(alias->args, iarg);
-        if (PyType_Check(arg)) {
-            int res = PyObject_IsInstance(instance, arg);
-            if (res < 0) {
-                return NULL;
-            }
-            if (res) {
-                Py_RETURN_TRUE;
-            }
-        }
-    }
-    Py_RETURN_FALSE;
-}
-
-static PyObject *
-union_subclasscheck(PyObject *self, PyObject *instance)
-{
-    if (!PyType_Check(instance)) {
-        PyErr_SetString(PyExc_TypeError, "issubclass() arg 1 must be a class");
-        return NULL;
-    }
-    unionobject *alias = (unionobject *)self;
-    if (!is_generic_alias_in_args(alias->args)) {
-        PyErr_SetString(PyExc_TypeError,
-            "issubclass() argument 2 cannot contain a parameterized generic");
-        return NULL;
-    }
-    Py_ssize_t nargs = PyTuple_GET_SIZE(alias->args);
-    for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
-        PyObject *arg = PyTuple_GET_ITEM(alias->args, iarg);
-        if (PyType_Check(arg)) {
-            int res = PyObject_IsSubclass(instance, arg);
-            if (res < 0) {
-                return NULL;
-            }
-            if (res) {
-                Py_RETURN_TRUE;
-            }
-        }
-    }
-    Py_RETURN_FALSE;
-}
-
 static PyObject *
 union_richcompare(PyObject *a, PyObject *b, int op)
 {
@@ -348,12 +294,6 @@ static PyMemberDef union_members[] = {
         {0}
 };
 
-static PyMethodDef union_methods[] = {
-        {"__instancecheck__", union_instancecheck, METH_O},
-        {"__subclasscheck__", union_subclasscheck, METH_O},
-        {0}};
-
-
 static PyObject *
 union_getitem(PyObject *self, PyObject *item)
 {
@@ -440,6 +380,19 @@ union_getattro(PyObject *self, PyObject *name)
     return PyObject_GenericGetAttr(self, name);
 }
 
+PyObject *
+_Py_union_args_for_check(PyObject *self, bool is_instance_check)
+{
+    PyObject *args = ((unionobject *) self)->args;
+    if (!is_generic_alias_in_args(args)) {
+        PyErr_Format(PyExc_TypeError,
+                     "%s() argument 2 cannot contain a parameterized generic",
+                     is_instance_check ? "isinstance" : "issubclass");
+        return NULL;
+    }
+    return args;
+}
+
 PyTypeObject _PyUnion_Type = {
     PyVarObject_HEAD_INIT(&PyType_Type, 0)
     .tp_name = "types.UnionType",
@@ -455,7 +408,6 @@ PyTypeObject _PyUnion_Type = {
     .tp_hash = union_hash,
     .tp_getattro = union_getattro,
     .tp_members = union_members,
-    .tp_methods = union_methods,
     .tp_richcompare = union_richcompare,
     .tp_as_mapping = &union_as_mapping,
     .tp_as_number = &union_as_number,