∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {X Y Z : C} (α : X ≅ Y) {f : X ⟶ Z} {g : Y ⟶ Z},
  (CategoryTheory.CategoryStruct.comp α.inv f = g) = (f = CategoryTheory.CategoryStruct.comp α.hom g)