Goal:
  
  A : Type
  B : Type
  f : A → B
  H : ∀ l : list A, nth_error (map f l) 0 = option_map f (nth_error l 0)
  l : list A
  ============================
   (nth_error (map f l) 1 = option_map f (nth_error l 1))


DEBUG:Going to execute:
solve
[ do
![ solve
 [ trivial | apply : eq_sym ; trivial ]
 | discriminate
 | contradiction
 | Ltac.split ]
| case not_locked_false_eq_true; Ltac.assumption
| match goal with
  | H:¬ _ |- _ => solve [ case H; trivial ]
  end ]