By ref and by pointer kills performance.

[Richard (Rikki) Andrew Cattermole]

After even more thinking, I'm reminded of an operator overload that I 
want for reference counting.

``opGoingIntoROM``.

The reason for reference counting is obvious, to turn off reference 
counting.

But it also applies here.

Having this knowledge on the monitor could turn off the actual 
lock/unlock mutation.

Okay this is compelling enough to report it.

https://issues.dlang.org/show_bug.cgi?id=24393

This is no longer an "I want". It's a genuine type guarantee issue of 
something we currently support.