open import Agda.Builtin.Nat data The {ℓ}{A : Set ℓ} : A → Set ℓ where the : (a : A) → The a _ : The 42 _ = the 42 toNat : ∀ {n : Nat} → The n → Nat toNat {n} _ = n test : Nat test = toNat (the 42) {-# COMPILE AGDA2LAMBOX test #-}