You use the macro ILOCPCONSTRAINTWRAPPER to wrap an existing instance of IlcConstraint when you want to use it within Concert Technology model objects. You must use the member function IloCPConstraintI::use to force extraction of an extractable or an array of extractables:

ILOCPCONSTRAINTWRAPPER1(IloFreqConstraint, solver, IloIntVarArray, _vars) {
  use(solver, _vars);
  return IlcFreqConstraint(solver, solver.getIntVarArray(_vars));
}

For more information on wrapping constraints for use with Concert Technology, see the documentation for the macro ILOCPCONSTRAINTWRAPPER and the class IloCPConstraintI in the IBM ILOG Solver Reference Manual.