Index: Objects/listobject.c
===================================================================
--- Objects/listobject.c	(revision 53047)
+++ Objects/listobject.c	(working copy)
@@ -2475,6 +2475,9 @@
 		if (slicelength <= 0) {
 			return PyList_New(0);
 		}
+		else if (step == 1) {
+			return list_slice(self, start, stop);
+		}
 		else {
 			result = PyList_New(slicelength);
 			if (!result) return NULL;
@@ -2522,6 +2525,12 @@
 		if (step == 1 && ((PySliceObject*)item)->step == Py_None)
 			return list_ass_slice(self, start, stop, value);
 
+		/* Make sure s[5:2] = [..] inserts at the right place:
+		   before 5, not before 2. */
+		if ((step < 0 && start < stop) ||
+		    (step > 0 && start > stop))
+			stop = start;
+
 		if (value == NULL) {
 			/* delete slice */
 			PyObject **garbage;
@@ -2543,12 +2552,16 @@
 				return -1;
 			}
 
-			/* drawing pictures might help
-			   understand these for loops */
+			/* drawing pictures might help understand these for
+			   loops. Basically, we memmove the parts of the
+			   list that are *not* part of the slice: step-1
+			   items for each item that is part of the slice,
+			   and then tail end of the list that was not
+			   covered by the slice */
 			for (cur = start, i = 0;
 			     cur < stop;
 			     cur += step, i++) {
-				Py_ssize_t lim = step;
+				Py_ssize_t lim = step - 1;
 
 				garbage[i] = PyList_GET_ITEM(self, cur);
 
@@ -2560,11 +2573,11 @@
 					self->ob_item + cur + 1,
 					lim * sizeof(PyObject *));
 			}
-
-			for (cur = start + slicelength*step + 1;
-			     cur < self->ob_size; cur++) {
-				PyList_SET_ITEM(self, cur - slicelength,
-						PyList_GET_ITEM(self, cur));
+			cur = start + slicelength*step;
+			if (cur < self->ob_size) {
+				memmove(self->ob_item + cur - slicelength,
+					self->ob_item + cur,
+					(self->ob_size - cur) * sizeof(PyObject *));
 			}
 
 			self->ob_size -= slicelength;
Index: Lib/test/list_tests.py
===================================================================
--- Lib/test/list_tests.py	(revision 53047)
+++ Lib/test/list_tests.py	(working copy)
@@ -179,8 +179,10 @@
         self.assertEqual(a, self.type2test(range(10)))
 
         self.assertRaises(TypeError, a.__setslice__, 0, 1, 5)
+        self.assertRaises(TypeError, a.__setitem__, slice(0, 1, 5))
 
         self.assertRaises(TypeError, a.__setslice__)
+        self.assertRaises(TypeError, a.__setitem__)
 
     def test_delslice(self):
         a = self.type2test([0, 1])