allow ExtensionClass change the im_self of PyMethodObject in Pyston

src/ExtensionClass/_ExtensionClass.c

@@ -925,18 +925,19 @@ PyECMethod_New_(PyObject *callable, PyObject *inst)
 
   if (PyMethod_Check(callable))
     {
-      // if (callable->ob_refcnt == 1)
-        // {
-          // Pyston change:
-          // Py_XDECREF(((PyMethodObject*)callable)->im_self);
-          // Py_XDECREF(PyMethod_Self((PyObject *)callable));
-          // Py_INCREF(inst);
-          // ((PyMethodObject*)callable)->im_self = inst;
-          // PyMethod_Self((PyObject *)callable) = inst;
-          // Py_INCREF(callable);
-          // return callable;
-        // }
-      // else
+      if (callable->ob_refcnt == 1)
+        {
+          // Pyston change: use new PyMethod_SetSelf API to do this
+          // in Pyston.
+          /* Py_XDECREF(((PyMethodObject*)callable)->im_self); */
+          /* Py_INCREF(inst); */
+          /* ((PyMethodObject*)callable)->im_self = inst; */
+          /* Py_INCREF(callable); */
+          /* return callable; */
+          PyMethod_SetSelf(callable, inst);
+          return callable;
+        }
+      else
         // Pyston change:
         return callable->ob_type->tp_descr_get(
                   callable, inst,