Trouble reproducing compilation error

[Xinok via Digitalmars-d-learn]

I'm currently receiving several errors when trying to compile 
this code with DMD 2.066 (beginning with RC1):

https://github.com/Xinok/XSort

The compiler throws an error because it's unable to deduce a type 
for the predicate in a few places. This repository compiles just 
fine in DMD 2.065 and earlier (more specifically, 2.066 beta 5 
and earlier). I'm very certain that this is a bug given that I 
never experienced this issue before.

However, I'm finding it impossible to reproduce the bug so I can 
file a bug report. I'm not sure what exactly is causing it or if 
there's something specific in the context of this code that's 
triggering it. The only thing that I can deduce is that, in each 
case, an instance variable is being compared to an array element, 
e.g.:

     int[] arr = [10, 20, 30];
     int value = arr[0];
     pred(value, arr[1]); // Instance variable compared to array 
element

This one is stumping me and I could use some help in tracking 
down this bug.