Goal:
  
  A : Type
  P : A → A → Type
  Q : A → A → Type
  x : A
  y : A
  l : list A
  l' : list A
  X : All2 (Trel_conj P Q) l l'
  a : P x y
  b : Q x y
  a0 : All2 P l l'
  b0 : All2 Q l l'
  ============================
   (All2 P l l')


DEBUG:Going to execute:
<Coq.Init.Tauto.find_cut>
            ltac:(fun id0 id1 X2 =>
                    assert X2; [ exact (id0 id1) | clear id0 ])
Level 2: evaluation returns
<coq-core.plugins.tauto::is_disj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := All2 Q l l'
of type
constr of type tacvalue

Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.