Is this a bug or I made some mistake?

[solidstate1991 via Digitalmars-d-learn]

Since I have some screenshots: 
https://twitter.com/EvilReptoid/status/770303804550021121

I needed a bitarray, that had some more capability than the one 
in std.bitmanip for collision detection. I could test a whole 
line with it at once if my predictions are right. However I 
couldn't do the array slicing effectively if that code doesn't 
work. Some idea?