Goal:
    A : Type  B : Type  C : Type  R : A → B → C → Type  H : True
  ============================
   (All3_nil = All3_nil)


DEBUG:Going to execute:
DepElim.do_intros H; DepElim.generalize_by_eqs H
Level 5: evaluation returns
DepElim.do_intros H; DepElim.generalize_by_eqs H; tac H
where
tac := fun hyp => DepElim.do_case hyp
       where
       id := H
       of type
       constr
of type
tacvalue
H := H
of type
constr of type tacvalue