Function point_in_rings 

pub fn point_in_rings(
    rings: &[Ring],
    longitude_e6: i32,
    latitude_e6: i32,
) -> bool

Exact integer point-in-polygon, boundary inclusive.

A point exactly on a boundary is inside. Two abutting regions therefore both claim their shared edge, which costs an operator one extra region in a list they are reviewing anyway; a gap between them would leave a position with no region at all.