{"ast_node_type":"other","tokens":[{"end":85,"kind":"keyword","start":0,"text":"debug!(\"{:?}"}]}
                        debug!("{:?} used_mut_upvars={:?}", def_id, used_mut_upvars);
                        let used_mut_upvars = self.root_cx.used_mut_upvars(def_id);
                        // FIXME: We're cloning the `SmallVec` here to avoid borrowing `root_cx`