∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] {X : C} {W Y Z : CategoryTheory.Over X} (f : W ⟶ Y)
  (g : W ⟶ Z), CategoryTheory.CategoryStruct.comp f.left Y.hom = CategoryTheory.CategoryStruct.comp g.left Z.hom