Goal:
  
  A : Type
  P : list A → list A → A → A → Type
  Q : list A → list A → A → A → Type
  h : All2_fold Q [] []
  ============================
   (let H := CoreTactics.block in
    let H0 := CoreTactics.block in
    All2_fold (λ (Γ Δ : list A) (x y : A), P Γ Δ x y × Q Γ Δ x y) [] [])


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 := h
of type
ident of type tacvalue

Level 2: evaluation returns
(needs_generalization id; DepElim.generalize_sig_dest id) || idtac
where
id := h
of type
ident of type tacvalue

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

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