∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] {X Y : C} {c : CategoryTheory.Limits.BinaryCofan X Y}
  (hc : CategoryTheory.Limits.IsColimit c) (x : CategoryTheory.Limits.BinaryFan (Opposite.op X) (Opposite.op Y)),
  (CategoryTheory.CategoryStruct.comp ((fun s => (hc.desc s.unop).op) x) c.inl.op).unop = x.fst.unop