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:
match goal with
           | |- ?T => change (let _ := CoreTactics.block in T)
           end