Function sidecar_try_saved 

#[doc(hidden)]
pub fn sidecar_try_saved<O, T>(
    saved: &Saved<'_, O>,
    index: usize,
    name: &'static str,
) -> Option<T>
where
    O: TypedExternal,
    T: TryFromSexp,
    <T as TryFromSexp>::Error: Display,

T’s Sidecar field index, named name, as the save saved kept it, or None when the save has no slot for it: a field added after the version that saved the object.

Called by the try_<field> getters #[derive(ExternalPtr)] generates for a type with a rebuild hook.

Panics

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