https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91780
--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> --- GCC 10.1 isn't using the deduction guide at all, it seems to prefer to deduce the class type using the zip(Containers...) constructor, which deduces non-reference types. If I change the deduction guide to: template <typename... Container_types> zip(Container_types&&... containers) -> zip<int>; Then GCC 10.1 still compiles it, because it doesn't use that guide anyway. Whereas GCC 10.2 gives an error, because it does deduce as zip<int> and so z.containers_[0]->i is invalid.
