Get contains.py working

src/capi/typeobject.cpp

@@ -1161,7 +1161,7 @@ static PyObject* slot_tp_del(PyObject* self) noexcept {
 
 PyObject* slot_sq_item(PyObject* self, Py_ssize_t i) noexcept {
     STAT_TIMER(t0, "us_timer_slot_sqitem", SLOT_AVOIDABILITY(self));
-    return getitemInternal<CAPI>(self, boxInt(i));
+    return getitemInternal<CAPI>(self, autoDecref(boxInt(i)));
 }
 
 /* Pyston change: static */ Py_ssize_t slot_sq_length(PyObject* self) noexcept {

src/runtime/classobj.cpp

@@ -1027,9 +1027,9 @@ static Box* instanceIter(BoxedInstance* self) {
     }
 
     if ((func = _instanceGetattribute(self, getitem_str, false)) == NULL) {
-        AUTO_DECREF(func);
         raiseExcHelper(TypeError, "iteration over non-sequence");
     }
+    Py_DECREF(func);
 
     Box* r = PySeqIter_New((PyObject*)self);
     if (!r)

test/tests/contains.py

-# expected: reffail
 class C(object):
     def __init__(self, x):
         self.x = x