∀ {C : Type u_1} [inst : CategoryTheory.EnrichedCategory CategoryTheory.Cat C] {a b : CategoryTheory.CatEnriched C}
  {f f' : a ⟶ b} (η : f ⟶ f'),
  CategoryTheory.CatEnriched.hComp η (CategoryTheory.CategoryStruct.id (CategoryTheory.CategoryStruct.id b)) =
    CategoryTheory.CategoryStruct.comp (CategoryTheory.eqToHom ⋯)
      (CategoryTheory.CategoryStruct.comp η (CategoryTheory.eqToHom ⋯))