{"ast_node_type":"variable","tokens":[{"end":74,"kind":"keyword","start":0,"text":"let"}]}
            let res = self.typeck_results().qpath_res(qpath, expr.hir_id);
        if let hir::ExprKind::Struct(qpath, fields, ref base) = expr.kind {
            let adt = self.typeck_results().expr_ty(expr).ty_adt_def().unwrap();