{"ast_node_type":"other","tokens":[{"end":73,"kind":"keyword","start":0,"text":"///"}]}
    /// later proving the `Subtype(?0, ?1)` goal from the first relation.
    /// first time we've related these types, this only happens when
    cache: DelayedSet<(ty::Variance, Ty<'tcx>, Ty<'tcx>)>,