pub type R_altrep_Unserialize_method_t = Option<unsafe extern "C" fn(arg1: SEXP, arg2: SEXP) -> SEXP>;
pub enum R_altrep_Unserialize_method_t { None, Some(unsafe extern "C" fn(*mut SEXPREC, *mut SEXPREC) -> *mut SEXPREC), }
No value.
Some value of type T.
T