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


DEBUG:Going to execute:
try (intro; CoreTactics.intros_until_block)