Function sidecar_r_get 

#[doc(hidden)]
pub unsafe fn sidecar_r_get<T: TypedExternal>(
    x: SEXP,
    index: usize,
    require_live: bool,
) -> SEXP

Reads T’s Sidecar field index from the external pointer x carries (sidecar_receiver).

Called by the R getters #[derive(ExternalPtr)] generates. A live struct’s pending value for the field is flushed into the slot first; a pointer without an address (after readRDS()) reads its protection list as is, unless require_live refuses it (checked_prot).

Panics

When x carries no external pointer to a T, or with the miniextendr_borrow_conflict R error while a running call holds the value mutably.

Safety

Must be called from R’s main thread with a valid x.