ext1 i
α : Type
inst✝¹ : Accessible α
rtr : α
inst✝ : Finite α
cpt : Component.Valued
vs : ID ⇀ Value
⊢ set rtr cpt vs[Component.val cpt] = fun i => do
    let x ← rtr[Component.val cpt][i]
    some (Option.getD (vs i) x)
case h
α : Type
inst✝¹ : Accessible α
rtr : α
inst✝ : Finite α
cpt : Component.Valued
vs : ID ⇀ Value
i : Component.idType (Component.val cpt)
⊢ set rtr cpt vs[Component.val cpt][i] = do
    let x ← rtr[Component.val cpt][i]
    some (Option.getD (vs i) x)