Goal:
  
  A : Type
  B : Type
  P : A → B → Prop
  p : A → B → bool
  Hp : ∀ (x : A) (y : B), reflect (P x y) (p x y)
  x : A
  y : B
  l : list A
  l' : list B
  H : P x y
  H0 : Forall2 P l l'
  IHForall2 : is_true (forallb2 p l l')
  ============================
   (p x y && forallb2 p l l' = true)


DEBUG:Going to execute:
solve
[ do
![ solve
 [ trivial | apply : eq_sym ; trivial ]
 | discriminate
 | contradiction
 | Ltac.split ]
| case not_locked_false_eq_true; Ltac.assumption
| match goal with
  | H:¬ _ |- _ => solve [ case H; trivial ]
  end ]