allout-range-overlaps is a compiled Lisp function in `allout-widgets.el'.

(allout-range-overlaps FROM TO RANGES)

Return a pair indicating overlap of FROM and TO subtree range in RANGES.

First element of result indicates whether candidate range FROM, TO
overlapped any of the existing ranges.

Second element of result is a new version of RANGES incorporating the
candidate range with overlaps consolidated.

FROM and TO must be in increasing order, as must be the pairs in RANGES.