Patch #1674228: when assigning a slice (old-style), check for the

sq_ass_slice instead of the sq_slice slot.
 (backport from rev. 54139)

Lib/test/test_descr.py

@@ -4143,6 +4143,19 @@ def notimplemented():
                 check(iexpr, c, N1)
                 check(iexpr, c, N2)
 
+def test_assign_slice():
+    # ceval.c's assign_slice used to check for
+    # tp->tp_as_sequence->sq_slice instead of
+    # tp->tp_as_sequence->sq_ass_slice
+
+    class C(object):
+        def __setslice__(self, start, stop, value):
+            self.value = value
+
+    c = C()
+    c[1:2] = 3
+    vereq(c.value, 3)
+
 def test_main():
     weakref_segfault() # Must be first, somehow
     wrapper_segfault()
@@ -4239,6 +4252,7 @@ def test_main():
     test_init()
     methodwrapper()
     notimplemented()
+    test_assign_slice()
 
     if verbose: print "All OK"
 

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 2.5.1c1?
 Core and builtins
 -----------------
 
+- Patch #1674228: when assigning a slice (old-style), check for the
+  sq_ass_slice instead of the sq_slice slot.
+
 - Bug #1669182: prevent crash when trying to print an unraisable error
   from a string exception.
 

Python/ceval.c

@@ -3926,7 +3926,7 @@ assign_slice(PyObject *u, PyObject *v, PyObject *w, PyObject *x)
 	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;