Goal:
  
  A : Type
  P : A → Prop
  Q : A → Prop
  a : A
  l : list A
  a0 : A
  l' : list A
  IHl : All P l → All Q l' → #|l| = #|l'| → All2 (λ x y : A, P x ∧ Q y) l l'
  ha : All P (a :: l)
  hb : All Q (a0 :: l')
  ============================
   (S #|l| = S #|l'| → All2 (λ x y : A, P x ∧ Q y) (a :: l) (a0 :: l'))


DEBUG:Going to execute:
match H' with
           | H => idtac
           end
Level 3: H'
 has value 
hb

Level 3: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.