message: Use preinstalled symbol
diff: @@ -35,7 +35,7 @@ RType RApiTypes::DetectRType(SEXP v, bool integer64) {
  return RType::UNKNOWN;
  }
  } else if (TYPEOF(v) == INTSXP && Rf_inherits(v, "difftime")) {
  - SEXP units = Rf_getAttrib(v, Rf_install("units"));
  + SEXP units = Rf_getAttrib(v, RStrings::get().units_sym);
  if (TYPEOF(units) != STRSXP) {
  return RType::UNKNOWN;
  }
  