Function lint_dead_codes 

fn lint_dead_codes<'tcx>(
    tcx: TyCtxt<'tcx>,
    target_lint: &'static Lint,
    module: LocalModDefId,
    live_symbols: &'tcx LocalDefIdSet,
    ignored_derived_traits: &'tcx LocalDefIdMap<FxIndexSet<DefId>>,
    free_items: impl Iterator<Item = ItemId>,
    foreign_items: impl Iterator<Item = ForeignItemId>,
)