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')
  ============================
   (is_true (p x y && true))


DEBUG:Going to execute:
done
Level 0: Backtrace:

No matching clauses for match.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 1: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
DEBUG LTAC Evaluated term: IHForall2
DEBUG LTAC Evaluated term: IHForall2
DEBUG LTAC Evaluated term: Prop
DEBUG LTAC Evaluated term: Prop