obtain ⟨n, rfl⟩ := h
case inr
α : Type
c : Clause α
x : List (Clause α)
h : ∃ n, x = List.replicate n []
⊢ Nonempty α ∨ ∃ n, [] :: x = List.replicate n []
case inr.intro
α : Type
c : Clause α
n : Nat
⊢ Nonempty α ∨ ∃ n_1, [] :: List.replicate n [] = List.replicate n_1 []