∀ (p₂ p₁ acc : Lean.Grind.CommRing.Poly),
  Lean.Grind.CommRing.Poly.mul.go p₂ p₁ acc =
    match p₁ with
    | Lean.Grind.CommRing.Poly.num k => acc.combine (Lean.Grind.CommRing.Poly.mulConst k p₂)
    | Lean.Grind.CommRing.Poly.add k m p₁ =>
      Lean.Grind.CommRing.Poly.mul.go p₂ p₁ (acc.combine (Lean.Grind.CommRing.Poly.mulMon k m p₂))