[Bug c++/63628] [c++1y] cannot use decltype on captured arg-pack

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63628

--- Comment #4 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Paolo Carlini from comment #3)
> The second and third variants work in mainline.

Yes, they were fixed by the patch for bug 68309.  We need a further fix to
handle the original testcase.