Design a procedural macro (#[derive(Keyed)]) for generatively enabling a structure to be indexed by its keys

[FL03]

Example

use scsys::Keyed;

#[derive(Debug, Keyed)]
#[scsys(key = S)]
pub struct Sample {
    a: usize,
    b: usize
}

fn main() {
    let sample = Sample { a: 10, b: 100 };
    assert_eq!(sample[S::A], &10);
}

[FL03]

One alternative consideration would to simply require stores to have public fields.