∀ {R : Type u} [inst : Ring R] {X : Type u} {M : ModuleCat R} {f g : (ModuleCat.free R).obj X ⟶ M},
  (∀ (x : X),
      (CategoryTheory.ConcreteCategory.hom f) (ModuleCat.freeMk x) =
        (CategoryTheory.ConcreteCategory.hom g) (ModuleCat.freeMk x)) →
    f = g