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


DEBUG:Going to execute:
use_hyps; do_ccl
Level 0: Backtrace:

Tactic failure: congruence failed.
Level 0: Backtrace:

Tactic failure: congruence failed.
Level 0: Backtrace:

No applicable tactic.