Goal:
  
  A : Type
  B : Type
  a : A
  l : list A
  b : B
  l' : list B
  IHl : ∀ l' : list B, #|l| = #|l'| → Forall2 (λ (_ : A) (_ : B), True) l l'
  ============================
   (S #|l| = S #|l'| → Forall2 (λ (_ : A) (_ : B), True) (a :: l) (b :: l'))


DEBUG:Going to execute:
<coq-core.plugins.ltac::auto@0> $1 $2 $3
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.