∀ {ι : Type u_1} {R : Type u_3} {A : ι → Type u_4} [inst : CommSemiring R]
  [inst_1 : (i : ι) → NonUnitalNonAssocSemiring (A i)] [inst_2 : (i : ι) → Module R (A i)]
  [inst_3 : ∀ (i : ι), SMulCommClass R (A i) (A i)] [inst_4 : ∀ (i : ι), IsScalarTower R (A i) (A i)]
  (x y : PiTensorProduct R fun i => A i), (PiTensorProduct.mul x) y = x * y