{η : Type u_5} →
  {α : Type u_6} →
    {ι : Type u_7} →
      {P : Sort u} →
        {idxFun : ι → α ⊕ η} →
          {proper : ∀ (e : η), ∃ i, idxFun i = Sum.inr e} →
            {idxFun' : ι → α ⊕ η} →
              {proper' : ∀ (e : η), ∃ i, idxFun' i = Sum.inr e} →
                { idxFun := idxFun, proper := proper } = { idxFun := idxFun', proper := proper' } →
                  (idxFun ≍ idxFun' → P) → P