Goal:
    A : Type  P : A → Type  Q : A → Type  Hl' : All Q []
  ============================
   (let H := CoreTactics.block in
    let H0 := CoreTactics.block in All (λ x : A, P x × Q x) [])


DEBUG:Going to execute:
needs_generalization id; DepElim.generalize_sig_dest id
Level 2: evaluation returns
(needs_generalization id; DepElim.generalize_sig_dest id) || idtac
where
id := Hl'
of type
constr of type tacvalue

Level 1: evaluation returns
(needs_generalization id; DepElim.generalize_sig_dest id) || idtac
where
id := Hl'
of type
constr of type tacvalue