Fixup Repeat condition

Fixup of #1895 : I just realized we needed two way conversion (for returning the value from mutable to qualified), and that `qualified : mutable` is not necessarily equivalent (say, as struct with a const alias this that returns a mutable).

I'm leaving on a 10 day leave, so I won't be able to reply for a little while. I also didn't have time to write a unittest for this. Sorry. Since this was a potential reg though, I figured it was important to submit it sooner rather than later.