Function consolidate 

pub fn consolidate<T, V, R: GetBeginEnd<T>, S: RangeBounds<T>, C: IncDecCpCmp<T, V>, F: GetBeginEndOption<T, R>, I: Iterator<Item = S>>(
    last: &mut Option<(R, Vec<(usize, S)>)>,
    iter: &mut I,
    t: &C,
    rebound: &V,
    f: &F,
    offset: usize,
) -> (usize, Option<RangeRelation<(R, Vec<(usize, S)>)>>)

This function is the stateless implementation of crate::Consolidate.