Function sidecar_get 

#[doc(hidden)]
pub fn sidecar_get<O, T>(
    ptr: &impl SidecarOwner<O>,
    index: usize,
    name: &'static str,
    field: fn(&O) -> &Sidecar<T>,
) -> T
where
    O: TypedExternal,
    T: IntoR + TryFromSexp,
    <T as TryFromSexp>::Error: Display,

Reads T’s Sidecar field index of the object ptr holds, after moving the field’s pending value into the slot.

Called by the getters #[derive(ExternalPtr)] generates (T::field(&ptr)); field selects the struct’s Sidecar field.

Panics

Off R’s main thread, naming the field, before touching R; or when the slot does not convert to T.