Function query_ensure_error_guaranteed 

pub(crate) fn query_ensure_error_guaranteed<'tcx, C, T>(
    tcx: TyCtxt<'tcx>,
    query: &'tcx QueryVTable<'tcx, C>,
    key: C::Key,
    ensure_mode: EnsureMode,
) -> Result<(), ErrorGuaranteed>
where
    C: QueryCache<Value = Erased<Result<T, ErrorGuaranteed>>>,
    Result<T, ErrorGuaranteed>: Erasable,

Shared implementation of tcx.ensure_ok().$query(..) for queries that have the return_result_from_ensure_ok modifier.