Function query_get_at 

pub(crate) fn query_get_at<'tcx, C>(
    tcx: TyCtxt<'tcx>,
    span: Span,
    query: &'tcx QueryVTable<'tcx, C>,
    key: C::Key,
) -> C::Value
where
    C: QueryCache,

Shared implementation of tcx.$query(..) and tcx.at(span).$query(..) for all queries.