(λ (x : ℕ), x) a + of_num b = 10 : Prop
@eq.{1} nat (@add.{0} nat nat.has_add ((λ (x : nat), x) a) (nat.of_num b))
  (@bit0.{0} nat nat.has_add
     (@bit1.{0} nat nat.has_one nat.has_add (@bit0.{0} nat nat.has_add (@one.{0} nat nat.has_one)))) :
  Prop