095bf01649
Because child > 0, the two statements are equivalent, but using saturating_sub and <= yields in faster code. This is most notable in the binary_heap::bench_into_sorted_vec benchmark, which shows a speedup of 1.26x, which uses sift_down_range internally. The speedup of pop (that uses sift_down_to_bottom internally) is much less significant as the sifting method is not called in a loop.