[PATCH] libstdc++: Work around C++20 tuple<tuple<any>> constraint recursion [PR116440]

[Ville Voutilainen]

On Thu, 13 Mar 2025 at 23:28, Patrick Palka <ppalka@redhat.com> wrote:
> > Oh, never mind. The pack is just deduced as an empty pack.
>
> Yep that's my understanding, though I don't know where in the standard
> this is specified, a quick Ctrl+F is failing me.

I'll go with https://eel.is/c++draft/temp.variadic#9, and in particular
https://eel.is/c++draft/temp.variadic#9.sentence-4

> I can use template<int = 0> or template<typename = void> if that's
> preferred :)

I think I would prefer template<typename=void>, that wouldn't cause
the pack-deduction
hallucinations. :)