Function scalar_charsxp_unchecked 

pub(crate) unsafe fn scalar_charsxp_unchecked(
    sexp: SEXP,
) -> Result<SEXP, SexpError>

Unchecked-FFI variant of scalar_charsxp — uses len_unchecked / string_elt_unchecked.

Safety

Must be called from R’s main thread (same contract as TryFromSexp::try_from_sexp_unchecked).