impl_scalar_property_reader! for usize?

[michaelkirk]

re: flatgeobuf/flatgeobuf#109 (comment)

let population: Option<usize> = feature.property("population");

It looks like there is no impl_scalar_property_reader! for usize.

In my specific use case, I realized it was inappropriate use of usize anyway, and switched to a u64, so everything is working for me.

Is usize something you want to support?

It seems somewhat fraught as a serializable type since it can have different size on different machines.

[pka]

I didn't think about it earlier, but I it shouldn't cause problems to support usize. Could be convenient sometimes.

[michaelkirk]

I trust that the code to support it could be written easily enough, but the question that arises is what happens when you serialize large values on platforms where usize is 64bit, and then deserialize on a platform where usize is 32bit?

protobuf doesn't support it: https://developers.google.com/protocol-buffers/docs/proto3#scalar
flatbuffer doesn't support it: https://google.github.io/flatbuffers/md__schemas.html
serde seemingly had, but then removed, support for it: serde-rs/serde#718

[pka]

Thanks for your research! You convinced me that it's better not to support a usize conversion.

Using feature.property::<u32>("population") as usize is probably good enough.

[michaelkirk]

I guess this turned into a please-never-have-this-Feature Request. 😅