Goal:
  
  A : Type
  P : A → Prop
  a : A
  l : list A
  l' : list A
  H0 : P a
  H1 : Forall P (l ++ l')
  H2 : Forall P l
  H3 : Forall P l'
  ============================
   (Forall P (a :: l))


DEBUG:Going to execute:
<Coq.Init.Tauto.flatten_contravariant_disj> flags X1 X2 id
Level 2: evaluation returns
<coq-core.plugins.tauto::flatten_contravariant_conj@0>
where
tauto_flags := 
of type
tauto_flags
id := P
of type
constr
X2 := Prop
of type
constr
X1 := A
of type
constr of type tacvalue

Level 2: Backtrace:

Tactic failure.
Level 2: Backtrace:

Tactic failure.
Level 1: Backtrace:

Tactic failure.