https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115476
--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
In check_trait_type, we do
if (kind == 1 && TREE_CODE (type) == ARRAY_TYPE && !TYPE_DOMAIN (type))
return true; // Array of unknown bound. Don't care about completeness.
and then end up crashing in record_has_unique_obj_representations:
4836 if (cur != wi::to_offset (sz))
because sz is null.
https://en.cppreference.com/w/cpp/types/has_unique_object_representations says
"The behavior is undefined if T is an incomplete type other than (possibly
cv-qualified) void or array of unknown bound."
