∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] {D : Type u₂} [inst_1 : CategoryTheory.Category.{v₂, u₂} D]
  [inst_2 : SizeOf C] [inst_3 : SizeOf D] (a : D), sizeOf (CategoryTheory.Join.right a) = 1 + sizeOf a