OK - that’s a case where both using a variable name like rng (or at least r) instead of i, and a type declaration ::AbstractRange would have helped a lot in making that code understandable.
Does garbage collection not have a problem with one string pointing into the middle of another like that?
If so, why even bother timing the fastslice function, if it’s not going to be useful at all in practice?
(it doesn’t seem to really be faster than making a SubString by the older rules though).