Goal:
    A : Type  l' : list A  v : nat  H : v < 0
  ============================
   (nth_error l' v = nth_error [] v)


DEBUG:Going to execute:
contradiction
Level 0: Backtrace:

Proof is not complete.
Level 0: Backtrace:

Proof is not complete.
Level 1: Backtrace:

Proof is not complete.
Level 0: Backtrace:

Proof is not complete.
Level 0: Backtrace:

Proof is not complete.