∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] (F G : CategoryTheory.Functor C (Type w)),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.FunctorToTypes.binaryProductIso F G).hom
      CategoryTheory.FunctorToTypes.prod.fst =
    CategoryTheory.Limits.prod.fst