∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {P Q : C} [inst_1 : CategoryTheory.Limits.HasZeroMorphisms C]
  [inst_2 : CategoryTheory.Limits.HasBinaryBiproduct P Q] [CategoryTheory.Projective P] [CategoryTheory.Projective Q],
  CategoryTheory.Projective (P ⊞ Q)