https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84768
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
oldelt is
<tree_list 0x7fffefd9f280 purpose <error_mark 0x7fffefc45e58> value
<error_mark 0x7fffefc45e58>>
It has been created in:
/* Add it to the list. */
if (parameter != error_mark_node)
parameter_list = process_template_parm (parameter_list,
parm_loc,
parameter,
is_non_type,
is_parameter_pack);
else
{
tree err_parm = build_tree_list (parameter, parameter);
parameter_list = chainon (parameter_list, err_parm);
}
which looks like it is intentional that way (r116661), so probably need to
handle error_mark_node somewhere else, maybe in build_deduction_guide?
