Goal:
  
  A : Type
  P : A → Prop
  a : A
  l : list A
  H : ∀ x : A, In x (a :: l) → P x
  IHl : (∀ x : A, In x l → P x) → Forall P l
  ============================
   (a = a ∨ In a l)


DEBUG:Going to execute:
solve [ Ltac.left; t_tauto_intuit | Ltac.right; t_tauto_intuit ]
Level 2: evaluation returns
<coq-core.plugins.tauto::is_disj@0>
where
tauto_flags := 
of type
tauto_flags
X1 := a = a ∨ In a l
of type
constr of type tacvalue