Goal:
    A : Type  v : A
  ============================
   ((∃ n : nat, hd_error (skipn n []) = Some v) → False)


DEBUG:Going to execute:
<coq-core.plugins.ltac::discriminate@0>
Level 0: Backtrace:

Cannot apply lemma eq_sym
Level 0: Backtrace:

Cannot apply lemma eq_sym
Level 0: Backtrace:

Cannot apply lemma eq_sym