Calling to!string with null std.typecons.Rebindable results in segfault

[ZombineDev via Digitalmars-d-learn]

Hi guys!

I'm implementing a mixin for sinking the values of all class 
members which can be used like this:

class MyFancyClassWithAlotOfMembers
{
   // Many members here...

   void toString(scope void delegate(const(char)[]) sink) const
   {
       import utils.prettyPrint;
       mixin(toStrBody); // <- Magic happens here
   }
}

Here is how I have implemented it:
https://github.com/ZombineDev/Chess2RT/blob/master/source/util/prettyprint.d

While doing so I stumbled on this bug:
http://dpaste.dzfl.pl/875844035550

My questions are:
1) Is this a Phobos bug indeed? If so I will file a bug report.
2) Is there a better way to workaround the bug (without the 
compiles __trait)?