When creating a
RangeMap from a list of ranges and values, there’s a possiblity that two
ranges will overlap. In this case, it’s a problem if they want to be associated to different
values (because we don’t know which value should be assigned to the intersection of the
ranges). An
OverlapError is the result of such a situation. It contains two members. The
first is a
RangeMap obtained by simply ignoring all the ranges that would cause a bad
overlap. The second is the collection of ranges that were ignored.