Goal:
  
  A : Type
  B : Type
  R : nat → A → B → Type
  n : nat
  x : A
  y : B
  l : list A
  r : list B
  r0 : R n x y
  a : All2i R (S n) l r
  ============================
   (eq_refl = eq_refl)


DEBUG:Going to execute:
repeat (simpl; DepElim.hnf_eq; DepElim.rewrite_refl_id);
            try progress autounfold with equations
Level 1: Backtrace:

Failed to progress.
Level 1: Backtrace:

Failed to progress.
Level 1: Backtrace:

Failed to progress.