Goal:
  
  A : Type
  P : list A → A → Type
  b : All_fold P []
  e : NoConfusionHom_All_fold A P [] (All_fold_nil P) b
  ============================
   (let H := CoreTactics.block in
    noConfusionHom_All_fold_obligation_2 A P [] (All_fold_nil P) b
      (noConfusionHom_All_fold_obligation_1 A P [] (All_fold_nil P) b e) = e)


DEBUG:Going to execute:
fun id =>
             CoreTactics.on_last_hyp
              ltac:(fun id' =>
                      match id' with
                      | id => idtac
                      | _ => revert id'; CoreTactics.revert_until id
                      end)