{"ast_node_type":"variable","tokens":[{"end":75,"kind":"keyword","start":0,"text":"if"}]}
        if let hir::ExprKind::Struct(qpath, fields, ref base) = expr.kind {
    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
            let res = self.typeck_results().qpath_res(qpath, expr.hir_id);