Goal:
    A : Type  n : nat  x : A  e : None = Some x
  ============================
   (S n < 0)


DEBUG:Going to execute:
contradiction
Level 1: Backtrace:

 The relation lt is not a declared symmetric relation. Maybe you need to require the Coq.Classes.RelationClasses library
Level 0: Backtrace:

 The relation lt is not a declared symmetric relation. Maybe you need to require the Coq.Classes.RelationClasses library
Level 0: Backtrace:

 The relation lt is not a declared symmetric relation. Maybe you need to require the Coq.Classes.RelationClasses library