Tracing out error that causes compiler crash

[solidstate1991]

During unittest in my own fork of std.experimental.xml (link: 
https://github.com/ZILtoid1991/experimental.xml ), potentially an 
error so severe is present, that it causes to crash the compiler 
(both DMD and LDC2, on Windows). I was able to separate the issue 
by commenting out all unittests, then re-enabling them one-by-one 
seeing when it crashes the compiler, but wasn't able to track 
down the issues. However, `domimpl.d` is a 2000+ line monster, 
with a huge templated class that nests multiple other classes. I 
suspect that there's some leftover from the stripped configurable 
allocator and/or error handler, that causes the issue.

At worst-case scenario, I can just manually rewrite the whole 
part (I already planned to write a more linear cursor for speed 
reasons), but that will consume a lot of my time. A lot of part 
of the code is already undocumented (especially anything 
non-public), so it's a question whether reimplementing stuff from 
almost zero, or trying to decipher a legacy code is the easier 
stuff.