∀ {C : Type u_3} [inst : CategoryTheory.Category.{u_1, u_3} C] {X Y Z : CategoryTheory.Limits.FormalCoproduct C}
  (f : X ⟶ Z) (g : Y ⟶ Z)
  (pb :
    (i : Function.Pullback f.f g.f) →
      CategoryTheory.Limits.PullbackCone (CategoryTheory.CategoryStruct.comp (f.φ (↑i).1) (CategoryTheory.eqToHom ⋯))
        (g.φ (↑i).2))
  (hpb : (i : Function.Pullback f.f g.f) → CategoryTheory.Limits.IsLimit (pb i))
  (s : CategoryTheory.Limits.PullbackCone f g),
  (↑((CategoryTheory.Limits.FormalCoproduct.homPullbackEquiv f g pb hpb s.pt).toFun
          ((CategoryTheory.Limits.FormalCoproduct.homPullbackEquiv f g pb hpb s.pt).invFun ⟨(s.fst, s.snd), ⋯⟩))).1 =
    (↑⟨(s.fst, s.snd), ⋯⟩).1