{"ast_node_type":"variable","tokens":[{"end":28,"kind":"keyword","start":0,"text":"let"}]}
        let mut file = None;
    fn suggest_missing_writer(&self, rcvr_ty: Ty<'tcx>, rcvr_expr: &hir::Expr<'tcx>) -> Diag<'_> {
        let mut err = struct_span_code_err!(