evVarsOfCallStack :: EvCallStack -> VarSet
evVarsOfCallStack cs = case cs of
  EvCsEmpty -> emptyVarSet
  EvCsTop _ _ tm -> evVarsOfTerm tm
  EvCsPushCall _ _ tm -> evVarsOfTerm tm
evVarsOfCallStack :: EvCallStack -> VarSet
evVarsOfCallStack cs = case cs of
  EvCsEmpty -> emptyVarSet
  EvCsTop _ _ tm -> evVarsOfTerm tm
  EvCsPushCall _ _ tm -> evVarsOfTerm tm
evVarsOfCallStack cs = case cs of
  EvCsEmpty -> emptyVarSet
  EvCsTop _ _ tm -> evVarsOfTerm tm
  EvCsPushCall _ _ tm -> evVarsOfTerm tm