[Bug c++/99904] ICE: in tsubst_pack_expansion, at cp/pt.c:13056

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99904

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:2e6e0d86a06389056d0e7fecc99c547420ad787a

commit r12-4229-g2e6e0d86a06389056d0e7fecc99c547420ad787a
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Oct 7 10:02:54 2021 -0400

    c++: variadic ttp constraint subsumption [PR99904]

    Here we're crashing when level-lowering the variadic constraint C<Ts...>
    on the template template parameter TT because tsubst_pack_expansion expects
    processing_template_decl to be set during a partial substitution.

            PR c++/99904

    gcc/cp/ChangeLog:

            * pt.c (is_compatible_template_arg): Set processing_template_decl
            around tsubst_constraint_info.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/concepts-ttp4.C: New test.