∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {X Y Z : C} (S : C) [inst_1 : CategoryTheory.OverClass X S]
  [inst_2 : CategoryTheory.OverClass Y S] [inst_3 : CategoryTheory.OverClass Z S] (f : X ⟶ Y) (g : Y ⟶ Z)
  [inst_4 : CategoryTheory.HomIsOver f S] [inst_5 : CategoryTheory.HomIsOver g S],
  CategoryTheory.CategoryStruct.comp (CategoryTheory.OverClass.asOverHom S f) (CategoryTheory.OverClass.asOverHom S g) =
    CategoryTheory.OverClass.asOverHom S (CategoryTheory.CategoryStruct.comp f g)