https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103105
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:e2c7070ac7740508a7c49bfee9f895e216a272d6 commit r12-8110-ge2c7070ac7740508a7c49bfee9f895e216a272d6 Author: Patrick Palka <ppa...@redhat.com> Date: Tue Apr 12 12:58:18 2022 -0400 c++: requires-expr in pack expansion using pack [PR103105] Here after dependent substitution of {Ts...} into the alias 'wrap', since we never partially instantiate a requires-expr, we end up with a requires-expr whose REQUIRES_EXPR_EXTRA_ARGS contains an ARGUMENT_PACK_SELECT (which just resolves to the parameter pack Ts). Then when hashing the resulting dependent specialization of A, we crash from iterative_hash_template_arg since it deliberately doesn't handle ARGUMENT_PACK_SELECT. Like in r12-7102-gdb5f1c17031ad8, it seems the right fix here is to resolve ARGUMENT_PACK_SELECT arguments before storing them into an extra args tree (such as REQUIRES_EXPR). PR c++/103105 gcc/cp/ChangeLog: * pt.cc (build_extra_args): Call preserve_args. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-requires29.C: New test. * g++.dg/cpp2a/concepts-requires29a.C: New test.
