https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91966
--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-9 branch has been updated by Jason Merrill <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:70ae61692245b5002f32454c8447655ad65a8535 commit r9-8450-g70ae61692245b5002f32454c8447655ad65a8535 Author: Jason Merrill <ja...@redhat.com> Date: Thu Apr 2 23:40:46 2020 -0400 c++: alias template and parameter packs (PR91966). In this testcase, when we do a pack expansion of count_better_mins<nums>, nums appears both in the definition of count_better_mins and as its template argument. The intent is that we get a expansion over pairs of elements of the pack, i.e. less<2,2>, less<2,7>, less<7,2>, .... But if we substitute into the definition of count_better_mins when parsing the template, we end up with sum<less<nums,nums>...>, which never gives us less<2,7>. We could deal with this by somehow marking up the use of 'nums' as an argument for 'num', but it's simpler to mark the alias as complex, so we need to instantiate it later with all its arguments rather than replace it early with its expansion. gcc/cp/ChangeLog 2020-04-03 Jason Merrill <ja...@redhat.com> PR c++/91966 * pt.c (complex_pack_expansion_r): New. (complex_alias_template_p): Use it.
