Goal:
  
  A : Type
  P : A → A → Type
  r : A
  r' : A
  X : All2 P [r] ([] ++ [r'])
  x : A
  y : A
  l : list A
  l' : list A
  X0 : P r r'
  X1 : All2 P [] []
  H0 : x = r
  H1 : l = []
  H : y = r'
  H3 : l' = []
  ============================
   (All2 P [] [] × P r r')


DEBUG:Going to execute:
f x
Level 2: evaluation returns
<coq-core.plugins.tauto::with_uniform_flags@0>
where
f := fun flags => <Coq.Init.Tauto.intuition_gen> flags tac
     where
     tac := auto
     of type
     tacvalue
of type
tacvalue of type tacvalue

Level 1: evaluation returns
<coq-core.plugins.tauto::with_uniform_flags@0>
where
f := fun flags => <Coq.Init.Tauto.intuition_gen> flags tac
     where
     tac := auto
     of type
     tacvalue
of type
tacvalue of type tacvalue