[Bug libstdc++/106676] [C++20] Automatic iterator_category detection misbehaves when `::reference` is an rvalue reference, refuses to accept a forward iterator

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106676

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Avi Kivity from comment #5)
> I believe this is causing application of std::views::transform() not to
> model the underlying view's category, since its iterators can't return an
> lvalue.

No, your code just has a bug, see
https://eel.is/c++draft/range.transform.iterator#2.sentence-1
"The member typedef-name iterator_category is defined if and only if Base
models forward_range."

So transform_view's iterator has no iterator_category for an input range.