public bool Visit(CallableHeader node)
        {
            _symStack.Push(); //this will be function local namespace
            var callable = new CallableSymbol(node.Name.ToString())
            {
                ReturnSymType = null
            };

            if (node.ReturnType != null)
            {
                node.ReturnType.Accept(this);
                callable.ReturnSymType = _symStack.FindType(node.ReturnType.ToString());
                _symStack.AddVariable(true, "result", callable.ReturnSymType);
            }

            foreach (var paramSection in node.ParamList)
            {
                paramSection.Accept(this);
                foreach (var parameter in paramSection.ParamList)
                {
                    callable.ParametersTypes.Add(new Tuple <string, SymType>(paramSection.ParamModifier,
                                                                             _symStack.FindIdentInScope(parameter.ToString()).VarSymType));
                }
            }

            callable.IsForward  = true;
            callable.Local      = _symStack.Pop();
            node.CallableSymbol = callable;
//            if (!_symStack.PrepareFunction(callable))
//            {
//                throw new Exception(string.Format("({0}, {1}) semantic error: duplicate declaration of {2} '{3}' ",
//                    node.Name.Token.Line, node.Name.Token.Column,
//                    callable.ReturnSymType == null ? "procedure" : "function",
//                    node.GetSignature()));
//            }

            return(true);
        }