Goal:
  
  A : Type
  f : nat → A
  n : nat
  i : nat
  hf : ∀ i j : nat, f i = f j → i = j
  IHn : In (f i) (unfold n f) → i < n
  H : In (f i) (unfold n f ++ [f n])
  ============================
   (locked false = true)


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