enum result {OK, FAIL};
interface call_in_complex_expression
{
  in result hello ();
  behavior
  {
    result f ()
    {
      return result.OK;
    }

    result g (result r)
    {
      return r;
    }

    result r = result.OK;
    on hello:
    {
      bool b = f () != result.OK;   // not allowed
      result r = g (f ());          // not allowed
      if (f () == g (result.OK))    // not allowed
        reply (result.OK);
      else if (f () != result.OK)
        reply (f ());
    }
  }
}

call-in-complex-expression.dzn:20:16: error: call used in a complex
    expression
call-in-complex-expression.dzn:21:21: error: call used in a complex
    expression
call-in-complex-expression.dzn:22:19: error: call used in a complex
    expression