Goal:
    A : Type  d : A  n : nat  v : A  H : d = v
  ============================
   (None = None ∧ v = d)


DEBUG:Going to execute:
repeat (do_intro; try do_atom)
Level 0: Backtrace:

Tactic failure: congruence failed.
Level 0: Backtrace:

Tactic failure: congruence failed.
Level 0: Backtrace:

No applicable tactic.