Polygon doesn't implement PointDistance (but LineString does)

[lnicola]

I guess this explains why I never understood how to use rstar...

[urschrei]

This needs point-in-polygon. See #984 (comment) for why this isn't easy: in short, a robust point-in-polygon implementation requires quite a lot of supporting code. We (obviously) have all of that in geo, and can't use it for geo-types because that would create a circular dependency. The alternative is copy-and-pasting everything that's required into private_utils.rs, which is not maintainable.

In short: #984 (comment) is still the most sensible approach, except that it causes a lot of other problems.

[lnicola]

I guess a future rewrite of geo based on geo-traits will solve this?

That said, maybe geo should lose the geo-types dependency? I think it's used in a couple of different ways:

• trait definitions (CoordNum)
• complex types returned by some algorithms (minimum_rotated_rect returns Polygon)
• "primitive" types used by some algorithms (Line, Point, Triangle)
• tests
• PreparedGeometry construction
• anything else?

So should geo even use Polygon or expose Polygon in its implementation or public API?