On Thu, 13 Mar 2025 at 23:16, Ville Voutilainen <ville.voutilai...@gmail.com> wrote: > > On Thu, 13 Mar 2025 at 23:03, Patrick Palka <ppa...@redhat.com> wrote: > > + // Defined as a template to work around PR libstdc++/116440. > > + template<class...> > > + constexpr explicit(!__convertible<const _Elements&...>()) > > + tuple(const _Elements&... __elements) > > I don't understand how a constructor template declared like this can > ever be called. The template parameter pack > can't be provided or deduced, and can't have a default. So we're > effectively making this signature always lose > overload resolution to the one that takes a pack of _UElements&&. > > Which may be fine. I can't head-compile a test that would fail in that > case. If any of the incoming argument isn't one > of _Elements, that constructor wins overload resolution anyway. If the > incoming arguments are exactly _Elements, that > constructor does the same thing as this one. I think.
Oh, never mind. The pack is just deduced as an empty pack.
