Function check_path_obstructed 

pub fn check_path_obstructed<SuccessorsFn>(
    origin: BlockPos,
    current_position: RelBlockPos,
    path: &VecDeque<Edge<BlockPos, MoveData>>,
    successors_fn: SuccessorsFn,
) -> Option<usize>
where
    SuccessorsFn: Fn(RelBlockPos) -> Vec<Edge<RelBlockPos, MoveData>>,

Checks whether the path has been obstructed, and returns Some(index) if it has been.

The index is of the first obstructed node.