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


DEBUG:Going to execute:
DepElim.do_intros H; DepElim.generalize_by_eqs H
Level 1: evaluation returns
DepElim.do_intros H; DepElim.generalize_by_eqs H; tac H
where
tac := fun hyp => DepElim.do_case hyp
       where
       id := a
       of type
       ident
of type
tacvalue
H := a
of type
ident of type tacvalue