when arguments are cells clear the locals slot (backport of #17927)
diff --git a/Python/ceval.c b/Python/ceval.c
index f427841..e59c39d 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -3403,10 +3403,14 @@
int arg;
/* Possibly account for the cell variable being an argument. */
if (co->co_cell2arg != NULL &&
- (arg = co->co_cell2arg[i]) != CO_CELL_NOT_AN_ARG)
+ (arg = co->co_cell2arg[i]) != CO_CELL_NOT_AN_ARG) {
c = PyCell_New(GETLOCAL(arg));
- else
+ /* Clear the local copy. */
+ SETLOCAL(arg, NULL);
+ }
+ else {
c = PyCell_New(NULL);
+ }
if (c == NULL)
goto fail;
SETLOCAL(co->co_nlocals + i, c);