Goal:
    x : V.t  s : VSet.t
  ============================
   (~ VSet.In x (VSet.remove x s))


DEBUG:Going to execute:
match goal with
           | |- context [ VSet.singleton ?t ] =>
                 VSetDecide.MSetDecideAuxiliary.abstract_term t
           | _:context [ VSet.singleton ?t ]
             |- _ => VSetDecide.MSetDecideAuxiliary.abstract_term t
           | |- context [ VSet.add ?t _ ] =>
                 VSetDecide.MSetDecideAuxiliary.abstract_term t
           | _:context [ VSet.add ?t _ ]
             |- _ => VSetDecide.MSetDecideAuxiliary.abstract_term t
           | |- context [ VSet.remove ?t _ ] =>
                 VSetDecide.MSetDecideAuxiliary.abstract_term t
           | _:context [ VSet.remove ?t _ ]
             |- _ => VSetDecide.MSetDecideAuxiliary.abstract_term t
           | |- context [ VSet.In ?t _ ] =>
                 VSetDecide.MSetDecideAuxiliary.abstract_term t
           | _:context [ VSet.In ?t _ ]
             |- _ => VSetDecide.MSetDecideAuxiliary.abstract_term t
           end
Level 1: Backtrace:

Tactic failure: no need to abstract a variable.
Level 2: Backtrace:

Tactic failure: no need to abstract a variable.
Level 2: Backtrace:

Tactic failure: no need to abstract a variable.
Level 1: Backtrace:

Tactic failure: no need to abstract a variable.
Level 2: Backtrace:

Tactic failure: no need to abstract a variable.
Level 2: Backtrace:

Tactic failure: no need to abstract a variable.
Level 1: Backtrace:

Tactic failure: no need to abstract a variable.
Level 0: Backtrace:

No matching clauses for match.