replace ho := Object.not_iff_obj?_none.mpr ho
α : Type
inst✝ : Hierarchical α
rtr : α
cpt : Component
i : ID
ho :
  rtr[cpt][match cpt with
      | Component.rtr => ↑i
      | Component.rcn => i
      | Component.val v => i] =
    none
⊢ rtr{cpt}{i} = none
α : Type
inst✝ : Hierarchical α
rtr : α
cpt : Component
i : ID
ho :
  ∀ (o : Component.type α cpt),
    ¬Object rtr cpt
        (match cpt with
        | Component.rtr => ↑i
        | Component.rcn => i
        | Component.val v => i)
        o
⊢ rtr{cpt}{i} = none