{"ast_node_type":"variable","tokens":[{"end":67,"kind":"keyword","start":0,"text":"let"}]}
        let final_upvar_tys = self.final_upvar_tys(closure_def_id);
        // Equate the type variables for the upvars with the actual types.
        debug!(?closure_hir_id, ?args, ?final_upvar_tys);