{"ast_node_type":"variable","tokens":[{"end":43,"kind":"keyword","start":0,"text":"let"}]}
    let span = tcx.def_span(opaque_def_id);
fn opaque_type_cycle_error(tcx: TyCtxt<'_>, opaque_def_id: LocalDefId) -> ErrorGuaranteed {
    let mut err = struct_span_code_err!(tcx.dcx(), span, E0720, "cannot resolve opaque type");