∀ {R : Type u} [inst : Semiring R] {S₁ : Type u_1} {S₂ : Type u_2} [inst_1 : SMul S₁ S₂] [inst_2 : SMulZeroClass S₁ R]
  [inst_3 : SMulZeroClass S₂ R] [IsScalarTower S₁ S₂ R], IsScalarTower S₁ S₂ (Polynomial R)