As expected, auto data = cast(ubyte[]) x"deadbeef"; works with -betterC, but auto data = cast(ubyte[]) hexString!"deadbeef"; does not.
That's just because -betterC is buggy and extremely incomplete (this is why I'm so annoyed that it is getting advertised, it is nowhere near ready for use). there's no reason why it shouldn't work once those bugs get fixed.
