split <;> rename_i h
g : CNF Nat
⊢ (if h : ∃ a, mem a g then relabel (fun i => if w : i < g.numLiterals then ⟨i, w⟩ else ⟨0, ⋯⟩) g
      else List.replicate (List.length g) []).unsat ↔
    g.unsat
case isTrue
g : CNF Nat
h : ∃ a, mem a g
⊢ (relabel (fun i => if w : i < g.numLiterals then ⟨i, w⟩ else ⟨0, ⋯⟩) g).unsat ↔ g.unsat

case isFalse
g : CNF Nat
h : ¬∃ a, mem a g
⊢ unsat (List.replicate (List.length g) []) ↔ g.unsat