Goal:
    z : t  hd : A.t  tl : list A.t  H : lt (hd :: tl) z
  ============================
   (let H := CoreTactics.block in let H0 := CoreTactics.block in lt [] z)


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