rfl
case e_val.e_val.e_a.left.a.refl
n : Nat
ih :
  ∀ (p : Fin n → Prop) [inst : DecidablePred p] (k : Fin (count p)) (i : { i // p i }),
    decodeSubtype p k = i ↔ encodeSubtype p i = k
p : Fin (n + 1) → Prop
inst : DecidablePred p
k : Fin (count p)
i✝ : { i // p i }
h0 : ¬p 0
i : Nat
hi : i + 1 < n + 1
hp : p ⟨i + 1, hi⟩
hk : ↑(encodeSubtype (fun i => p i.succ) ⟨⟨i, ⋯⟩, hp⟩) < count p
h : encodeSubtype p ⟨⟨i + 1, hi⟩, hp⟩ = ⟨↑(encodeSubtype (fun i => p i.succ) ⟨⟨i, ⋯⟩, hp⟩), hk⟩
⊢ ↑(encodeSubtype (fun i => p i.succ) ⟨⟨i, ⋯⟩, hp⟩) = ↑⟨↑(encodeSubtype (fun i => p i.succ) ⟨⟨i, ⋯⟩, hp⟩), ⋯⟩
no goals