{"ast_node_type":"variable","tokens":[{"end":42,"kind":"keyword","start":0,"text":"let"}]}
                    let upcast_trait_ref =
                    let upcast_poly_trait_ref = this.upcast(original_poly_trait_ref, trait_def_id);
                        this.instantiate_binder_with_fresh_vars(upcast_poly_trait_ref);