∀ {α : Type u} {β : α → Type v} [inst : Ord α] {k : α → Ordering} (k' : α) (v' : β k')
  (hcmp : ∀ [Std.OrientedOrd α], k k' = Ordering.eq),
  Std.DTreeMap.Internal.Cell.ofEq k' v' hcmp = { inner := some ⟨k', v'⟩, property := ⋯ }