{"ast_node_type":"variable","tokens":[{"end":99,"kind":"keyword","start":0,"text":"let"}]}
                    let upcast_poly_trait_ref = this.upcast(original_poly_trait_ref, trait_def_id);
                    let original_poly_trait_ref = principal.with_self_ty(this.tcx, object_ty);
                    let upcast_trait_ref =