Function get_known_std_names 

fn get_known_std_names<'tcx>(
    tcx: TyCtxt<'tcx>,
    def_id: DefId,
) -> Option<Vec<String>>

Look up known argument names for standard-library APIs.

The lookup key is the public DefId path (see public_def_path). When no names are recorded the list is filled with numeric defaults ("0", "1", …).