∀ (R : Type u_1) {S : Type u_2} {A : Type u_3} {B : Type u_4} [inst : Monoid R] [inst_1 : Monoid S] [inst_2 : Star A]
  [inst_3 : Star B] [inst_4 : NonUnitalNonAssocSemiring A] [inst_5 : NonUnitalNonAssocSemiring B]
  [inst_6 : MulAction R S] [inst_7 : DistribMulAction S A] [inst_8 : DistribMulAction S B]
  [inst_9 : DistribMulAction R A] [inst_10 : DistribMulAction R B] [inst_11 : IsScalarTower R S A]
  [inst_12 : IsScalarTower R S B], Function.Injective (NonUnitalStarAlgHom.restrictScalars R)