{"ast_node_type":"function","tokens":[{"end":72,"kind":"keyword","start":0,"text":"fn"}]}
    fn check_for_self_assign(&mut self, assign: &'tcx hir::Expr<'tcx>) {
    #[allow(dead_code)] // FIXME(81658): should be used + lint reinstated after #83171 relands.
        fn check_for_self_assign_helper<'tcx>(