Goal:
  
  A : Type
  B : Type
  C : Type
  D : Type
  R : C → D → Type
  f : A → C
  g : B → D
  H : All2 R [] []
  ============================
   (let H := CoreTactics.block in
    let H0 := CoreTactics.block in
    All2 (λ (x : A) (y : B), R (f x) (g 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 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

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