Goal:
    A : Type  P : list A → A → Type  b : All_fold P []
  ============================
   (let H := CoreTactics.block in
    NoConfusionHom_All_fold A P [] (All_fold_nil P) b
    → let H0 := CoreTactics.block in All_fold_nil P = b)


DEBUG:Going to execute:
needs_generalization id; DepElim.generalize_sig_dest id
Level 4: evaluation returns
(needs_generalization id; DepElim.generalize_sig_dest id) || idtac
where
id := b
of type
constr of type tacvalue

Level 4: evaluation returns
(needs_generalization id; DepElim.generalize_sig_dest id) || idtac
where
id := b
of type
constr of type tacvalue

Level 3: evaluation returns
(needs_generalization id; DepElim.generalize_sig_dest id) || idtac
where
id := b
of type
constr of type tacvalue

Level 3: evaluation returns
(needs_generalization id; DepElim.generalize_sig_dest id) || idtac
where
id := b
of type
constr of type tacvalue