Goal:
    A : Type  v : A  _a_ : A  _l_ : list A  p : Some _a_ = Some v
  ============================
   (_a_ = v ∨ ∃ n : nat, hd_error (skipn n _l_) = Some v)


DEBUG:Going to execute:
match goal with
           | H:¬ _ |- _ => solve [ case H; trivial ]
           end
Level 1: Backtrace:

No such assumption.
Level 0: Backtrace:

No such assumption.
Level 0: Backtrace:

No such assumption.
Level 0: Backtrace:

No such assumption.