∀ {M : Type u_1} {N : Type u_2} {A : Type u_3} {B : Type u_4} [inst : AddZeroClass A] [inst_1 : AddZeroClass B]
  [inst_2 : DistribSMul M B] [inst_3 : DistribSMul N B] [SMulCommClass M N B], SMulCommClass M N (A →+ B)