Goal:
  
  A : Type
  B : Type
  P : nat → B → B → Type
  f : A → B
  i : nat
  hd : A
  tl : list A
  tl' : list A
  X : OnOne2i (λ i : nat, on_Trel (P i) f) (S i) tl tl'
  IHX : OnOne2i P (S i) (map f tl) (map f tl')
  ============================
   (OnOne2i P (S i) (map f tl) (map f tl'))


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

Tactic failure: congruence failed.
Level 0: Backtrace:

Tactic failure: congruence failed.