[Pitch] `@OptionSet` macro

[gwendal.roue (Gwendal Roué)]

@bbrk24

I have yet to see a good justification for why static key paths are illegal, though.

Key path cannot refer to static member

@DevAndArtist has a good memory—I tried to include this in SE-0254, but it wasn't the primary thrust of the proposal and I didn't finish implementing it in the limited time I could devote to a stretch goal. It seems totally doable, and might even be easy for someone who knows IRGen better than me—it just requires a lot of little corrections throughout the compiler. (When I stopped, I was in IRGen and still needed to make resilience work.) I'm not a core team member, but I suspect that if there …