Goal:
  
  A : Type
  f : nat → A
  m : nat
  n : nat
  t : A
  IHm : ∀ n : nat, nth_error (unfold m f) n = Some t → t = f n
  H : n < m + 1
  n0 : n ≠ m
  ============================
   (nth_error (unfold m f) n = Some t → t = f n)


DEBUG:Going to execute:
done
Level 1: Backtrace:

Proof is not complete.
Level 1: Backtrace:

Proof is not complete.
Level 1: Backtrace:

Proof is not complete.
Level 1: Backtrace:

Proof is not complete.
Level 1: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No matching clauses for match.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
Level 1: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.
DEBUG LTAC Evaluated term: Prop
DEBUG LTAC Evaluated term: Prop