Backport 52621:
Bug #1588287: fix invalid assertion for `1,2` in debug builds.
diff --git a/Python/ast.c b/Python/ast.c
index 52c098f..6551063 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -538,6 +538,7 @@
 	   || TYPE(n) == listmaker
 	   || TYPE(n) == testlist_gexp
 	   || TYPE(n) == testlist_safe
+	   || TYPE(n) == testlist1
 	   );
 
     seq = asdl_seq_new((NCH(n) + 1) / 2, c->c_arena);