[Bug c++/89642] gcc rejects valid implicit typename context in cast

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89642

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC, ICC, clang and MSVC all reject this at -std=c++20 (or /std:c++latest for
MSVC).