[Bug libstdc++/109049] std::declval gives wrong result for cv void

[de34 at live dot cn via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109049

--- Comment #3 from Jiang An <de34 at live dot cn> ---
I've mailed to LWG Chair to request legitimation of libc++ and libstdc++'s
current strategy.