Goal:
    A : Type  P : list A → A → Type  l : list A  a : All_fold P l
  ============================
   (let H := CoreTactics.block in
    noConfusionHom_All_fold_obligation_1 A P l a a
      (noConfusionHom_All_fold_obligation_2 A P l a a eq_refl) = eq_refl)


DEBUG:Going to execute:
CoreTactics.block_goal
Level 7: evaluation returns
idtac of type tacvalue

Level 5: evaluation returns
idtac of type tacvalue

Level 4: evaluation returns
idtac of type tacvalue