Add failing tests to try to confirm a suspected bug

[drewlesueur]

(Hopefully this is helpful)
I added some tests that I think should pass and some of them end up failing.

I tried to actually fix the issue. I got some test to pass, but I ended up breaking other tests, so I removed my attempt to fix.
My attempt was related to this code I found here: https://rosettacode.org/wiki/Ray-casting_algorithm#Go

for p.y == a.y || p.y == b.y {
        p.y = math.Nextafter(p.y, math.Inf(1))
}

I am not very familiar with the algorithm though.

PS, Thanks for the code. Tile38 looks really interesting.

[tidwall]

Hi Drew,

Thanks a bunch for finding this bug. Sorry about my broken code. :(

Typically a raycast can only help to determine if a point is fully inside a polygon, but I need to also detect if a point is on a segment of a polygon. I made some modification based on your suggested code. It's likely a little slower than the previous, but it should work now.

Please test it out on your side and let me know what you think.

[drewlesueur]

Thank you!
This also fixes my real-world test on my side.

[tidwall]

That's great to hear. 👍