{"ast_node_type":"variable","tokens":[{"end":57,"kind":"keyword","start":0,"text":"let"}]}
    let impl_predicates = tcx.predicates_of(impl_def_id);
    let impl_generics = tcx.generics_of(impl_def_id);
    let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).map(ty::EarlyBinder::instantiate_identity);