Factor-out common code with a new macro

Include/setobject.h

@@ -73,6 +73,8 @@ PyAPI_DATA(PyTypeObject) PyFrozenSet_Type;
 	(Py_TYPE(ob) == &PySet_Type || Py_TYPE(ob) == &PyFrozenSet_Type || \
 	  PyType_IsSubtype(Py_TYPE(ob), &PySet_Type) || \
 	  PyType_IsSubtype(Py_TYPE(ob), &PyFrozenSet_Type))
+#define PySet_Check(ob) \
+	(Py_TYPE(ob) == &PySet_Type || PyType_IsSubtype(Py_TYPE(ob), &PySet_Type))
 
 PyAPI_FUNC(PyObject *) PySet_New(PyObject *);
 PyAPI_FUNC(PyObject *) PyFrozenSet_New(PyObject *);

Objects/setobject.c

@@ -2158,7 +2158,7 @@ PySet_Size(PyObject *anyset)
 int
 PySet_Clear(PyObject *set)
 {
-	if (!PyType_IsSubtype(Py_TYPE(set), &PySet_Type)) {
+	if (!PySet_Check(set)) {
 		PyErr_BadInternalCall();
 		return -1;
 	}
@@ -2178,7 +2178,7 @@ PySet_Contains(PyObject *anyset, PyObject *key)
 int
 PySet_Discard(PyObject *set, PyObject *key)
 {
-	if (!PyType_IsSubtype(Py_TYPE(set), &PySet_Type)) {
+	if (!PySet_Check(set)) {
 		PyErr_BadInternalCall();
 		return -1;
 	}
@@ -2229,7 +2229,7 @@ _PySet_NextEntry(PyObject *set, Py_ssize_t *pos, PyObject **key, long *hash)
 PyObject *
 PySet_Pop(PyObject *set)
 {
-	if (!PyType_IsSubtype(Py_TYPE(set), &PySet_Type)) {
+	if (!PySet_Check(set)) {
 		PyErr_BadInternalCall();
 		return NULL;
 	}
@@ -2239,7 +2239,7 @@ PySet_Pop(PyObject *set)
 int
 _PySet_Update(PyObject *set, PyObject *iterable)
 {
-	if (!PyType_IsSubtype(Py_TYPE(set), &PySet_Type)) {
+	if (!PySet_Check(set)) {
 		PyErr_BadInternalCall();
 		return -1;
 	}