Make __mro__ a getter.

Author: ericsnowcurrently

Objects/typeobject.c

@@ -632,7 +632,6 @@ static PyMemberDef type_members[] = {
     {"__base__", T_OBJECT, offsetof(PyTypeObject, tp_base), READONLY},
     {"__dictoffset__", T_PYSSIZET,
      offsetof(PyTypeObject, tp_dictoffset), READONLY},
-    {"__mro__", T_OBJECT, offsetof(PyTypeObject, tp_mro), READONLY},
     {0}
 };
 
@@ -876,6 +875,12 @@ clear_mro(PyTypeObject *type)
     Py_CLEAR(type->tp_mro);
 }
 
+static PyObject *
+type_get_mro(PyTypeObject *type, void *context)
+{
+    return Py_NewRef(get_mro(type));
+}
+
 static PyTypeObject *best_base(PyObject *);
 static int mro_internal(PyTypeObject *, PyObject **);
 static int type_is_subtype_base_chain(PyTypeObject *, PyTypeObject *);
@@ -1249,6 +1254,7 @@ static PyGetSetDef type_getsets[] = {
     {"__name__", (getter)type_name, (setter)type_set_name, NULL},
     {"__qualname__", (getter)type_qualname, (setter)type_set_qualname, NULL},
     {"__bases__", (getter)type_get_bases, (setter)type_set_bases, NULL},
+    {"__mro__", (getter)type_get_mro, NULL, NULL},
     {"__module__", (getter)type_module, (setter)type_set_module, NULL},
     {"__abstractmethods__", (getter)type_abstractmethods,
      (setter)type_set_abstractmethods, NULL},