Goal:
    A : Type  n : nat  hd : A  tl : list A  H : S n < #|hd :: tl|
  ============================
   (S n ≤ #|tl|)


DEBUG:Going to execute:
Tactics.destruct_one_ex
Level 1: Backtrace:

No matching clauses for match.
Level 0: Backtrace:

No matching clauses for match.