So for executing static Rust functions we do have "full" support via the `Value::BuiltinFunction` type. We have an internal "BuiltinFunctionBuilder" type for cr

So for executing static Rust functions we do have "full" support via the `Value::BuiltinFunction` type. We have an internal "BuiltinFunctionBuilder" type for creating these conveniently (mostly) at compile time, and we have some external helper functions for creating them at runtime. As for calling methods on a Rust singleton / struct, that is not yet really supported. We do have a `Value::EmbedderObject` type that will be the place for these, but its implementation is so far entirely empty / todo!() only. The first step for those will be just a very plain and simple `Box<dyn ObjectMethods>` type of thing, but eventually I'm thinking that our EmbedderObjects would actually become backed by an ECS data storage in the engine heap. So eg. your Bar type would be registered to the engine via some call together with its fields, and those would form an ECS "archetype". Then these items would be created by another call and would then become visible to JS code as objects, with some of their fields possibly being pointers to foreign heap data etc. But that's a little ways off.