∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] {D : Type u₂} [inst_1 : CategoryTheory.Category.{v₂, u₂} D]
  {T : D} {S : CategoryTheory.Functor C D}, (CategoryTheory.CostructuredArrow.proj S T).Faithful