Goal:
  
  A : Type
  P : A → Type
  p : A → bool
  q : A → bool
  x : A
  l : list A
  p0 : P x
  X : All P l
  H : ∀ x : A, P x → p x = q x
  H0 : forallb p l = forallb q l
  ============================
   (p x && forallb p l = q x && forallb q l)


DEBUG:Going to execute:
<Coq.Init.Tauto.is_empty> flags X1; elim H
Level 3: evaluation returns
<coq-core.plugins.tauto::is_empty@0>
where
tauto_flags := 
of type
tauto_flags
X1 := ∀ x : A, P x → p x = q x
of type
constr of type tacvalue

Level 3: Backtrace:

Tactic failure.
Level 3: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.