Patch #1674228: when assigning a slice (old-style), check for the
sq_ass_slice instead of the sq_slice slot.
(backport from rev. 54139)
diff --git a/Python/ceval.c b/Python/ceval.c
index 1ee0f3b..690b2be 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -3926,7 +3926,7 @@
PyTypeObject *tp = u->ob_type;
PySequenceMethods *sq = tp->tp_as_sequence;
- if (sq && sq->sq_slice && ISINDEX(v) && ISINDEX(w)) {
+ if (sq && sq->sq_ass_slice && ISINDEX(v) && ISINDEX(w)) {
Py_ssize_t ilow = 0, ihigh = PY_SSIZE_T_MAX;
if (!_PyEval_SliceIndex(v, &ilow))
return -1;