Goal:
  
  A : Type
  P : A → Type
  Q : A → Type
  x : A
  l : list A
  p : P x
  Hl : All P l
  Hl' : All Q (x :: l)
  IHHl : All Q l → All (λ x : A, P x × Q x) l
  ============================
   (All (λ x : A, P x × Q x) (x :: l))


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

Level 3: Backtrace:

No matching clauses for match.
Level 2: Backtrace:

No matching clauses for match.