Goal:
    A : Type  P : list A → list A → A → A → Type  Q : list A → A → Type
  ============================
   (All_fold Q [])


DEBUG:Going to execute:
<Coq.Init.Tauto.is_disj> flags X1; (solve
            [ Ltac.left; t_tauto_intuit | Ltac.right; t_tauto_intuit ])