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
  ============================
   (locked false = true)


DEBUG:Going to execute:
Ltac.assumption
DEBUG LTAC Evaluated term: not_locked_false_eq_true