Strange _xopEquals function

[L!ort]

I downloaded druntime from 
https://github.com/xomboverlord/xomb-bare-bones/tree/master. It's 
druntime made for bare bones XOmB OS. If I want to compile it to 
library, dmd return error "undefined identifier _xopEquals". Then 
I  looked to official druntime and I found function _xopEquals. 
When I add this function to XOmB druntime, nothing changed 
(yielding undefined identifier _xopEquals did you mean function 
_xopEquals? ... funny error)...And second question, is there any 
documentation for druntime? And I don't mean source code ...