Goal:
    A : Type  B : Type  f : nat → A → B  l : list A
  ============================
   (mapi_rec (λ (k : nat) (x : A), f (Nat.pred #|l| - k) x) (List.rev l) 0 =
    mapi_rec (λ (k : nat) (x : A), f (Nat.pred #|l| - k) x) (List.rev l) 0)


DEBUG:Going to execute:
easy0 || (solve [ intuition eauto  3 with core terms ])