WIP Implement area functions on geometry traits

[kylebarron]

Change list

• Remove Send + Sync restriction on T on the trait. I don't know whether this restriction makes sense here. I originally added it because rust-postgis included it. But it appeared that CoordFloat doesn't include those trait bounds so it was easier in this context to remove them.
• Add fully parametrized T: CoordNum on each trait, and define other item types in terms of T. I needed to do this so that some algorithms could enforce CoordFloat and not just CoordNum.
  I'm not sure if type ItemType = LineString<Self::T>; on the impl is necessary instead of type ItemType = LineString<T>;.
• Implement pure functions for most combinations of geometry type + signed/unsigned area.
• Drop 1.63 CI from this branch

Questions:

• Is there a simple way with lifetimes to fix this temporary value dropped while borrowed error? It's on this line. I'm not sure if this is an issue with the trait design or implementation or with my code

[frewsxcv]

Is there a simple way with lifetimes to fix this temporary value dropped while borrowed error? It's on this line. I'm not sure if this is an issue with the trait design or implementation or with my code

When I run into situations like this, I typically start incrementally loosening lifetime bounds that don't need to be explicitly specified. With these changes, your code compiles: https://gist.github.com/frewsxcv/75e719227b889ee2930ccb59930b26de

[kylebarron]

I switched these to not use -= to avoid having to require the SubAssign type on T. Maybe requiring SubAssign and similar is such a low bar that we should require it?

[kylebarron]

When I run into situations like this, I typically start incrementally loosening lifetime bounds that don't need to be explicitly specified. With these changes, your code compiles: gist.github.com/frewsxcv/75e719227b889ee2930ccb59930b26de

Thanks! That was helpful! I was able to make some progress. But it seems like the trait methods that really need &'a self are the iterators.

So I can make progress by removing 'a everywhere but that forces me to write ugly code and avoid using the iterators, doing stuff like

for polygon_idx in 0..geom.num_polygons() {

Especially with the GeometryCollection and Geometry traits, it gets complex and it's not clear to me we can fully remove the lifetimes.

I tried to implement unsigned_area_geometry which takes anything that implements GeometryTrait, but there as_type requires 'a.

[frewsxcv]

This can now be:

type LineString<'a>: 'a + LineStringTrait<'a, T = Self::T>;

Or something like that

[kylebarron]

What's the benefit to adding <'a> onto the type name as well?

[frewsxcv]

You can remove the lifetime from the trait itself, which means any references to the trait don't need to specify that lifetime. Similar to https://github.com/georust/geo/pull/908/files

[kylebarron]

Oh wow that is super nice!

[kylebarron]

It ended up being a lot more work than expected but I implemented that change in geoarrow/geoarrow-rs#253 (I'm incubating and testing out trait impls there); I'll make a PR to the traits branch with those updated changes

(I still had lifetime issues connecting to geos but that's life 🤷‍♂️ )

[frewsxcv]

From what I understand, #1115 is a newer version of this so I'm going to close this one. Feel free to reopen if this is wrong