[Bug libstdc++/115218] The conversion constructor of concat_view::iterator always default-constructs variant

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115218

--- Comment #11 from Patrick Palka <ppalka at gcc dot gnu.org> ---
(In reply to Patrick Palka from comment #10)
> (In reply to 康桓瑋 from comment #9)
> > (In reply to Patrick Palka from comment #8)
> > > Fixed, thanks!
> > 
> > The fix for LWG 4082 is the missing viewable_range constraint for one pack
> > case.
> Where does that constraint come from? Since views::concat is "just" a CPO,
> not a range adaptor object, I don't think viewable_range is implied?
Ah, I think it's implied from the use of views::all.