So this is not acceptable?
let mainStageTonight: Set<ComparableMusicPerformer> = [
.init(FreddieMerqurie()),
.init(JimmyHendrix()),
]
struct ComparableMusicPerformer: Hashable, Comparable {
private var storage: MusicPerformer
statuc func ==(lhs: Self, rhs: Self) -> Bool { ... }
...
}