private void VisitNullConstNode(null_const_node expr)
 {
     
 }
            public expression_node convert_delegates_to_delegates(location call_location, expression_node[] parameters)
            {
                if (parameters.Length != 1)
                {
                    throw new PascalABCCompiler.TreeConverter.CompilerInternalError("Invalid delegates convertion");
                }
                delegate_internal_interface dii_to=
                    (delegate_internal_interface)_to.get_internal_interface(internal_interface_kind.delegate_interface);
                delegate_internal_interface dii =
                    (delegate_internal_interface)parameters[0].type.get_internal_interface(internal_interface_kind.delegate_interface);

                expression_node pr = parameters[0];

                base_function_call ifnotnull = null;
                if (_to.semantic_node_type == semantic_node_type.compiled_type_node)
                {
                    ifnotnull = new compiled_constructor_call((compiled_constructor_node)dii_to.constructor, call_location);
                }
                else
                {
                    ifnotnull = new common_constructor_call((common_method_node)dii_to.constructor, call_location);
                }
                //ccc = new common_constructor_call(dii_to.constructor, call_location);

                expression_node par = null;
                if (parameters[0].type.semantic_node_type == semantic_node_type.compiled_type_node)
                {
                    par = new compiled_function_call((compiled_function_node)dii.invoke_method, parameters[0], call_location);
                }
                else
                {
                    par = new common_method_call((common_method_node)dii.invoke_method, parameters[0], call_location);
                }
                ifnotnull.parameters.AddElement(par);

                null_const_node ncn = new null_const_node(_to, call_location);
                null_const_node ncn2 = new null_const_node(_to, call_location);

                PascalABCCompiler.TreeConverter.SymbolInfo si = pr.type.find_in_type(PascalABCCompiler.TreeConverter.compiler_string_consts.eq_name);

                basic_function_node fn = si.sym_info as basic_function_node;
                expression_node condition = null;
                if (fn != null)
                {
                    basic_function_call condition_bfc = new basic_function_call(fn, call_location);
                    condition_bfc.parameters.AddElement(pr);
                    condition_bfc.parameters.AddElement(ncn);
                    condition = condition_bfc;
                }
                else if (si.sym_info is compiled_function_node)
                {
                    compiled_static_method_call condition_cfc = new compiled_static_method_call(si.sym_info as compiled_function_node, call_location);
                    condition_cfc.parameters.AddElement(pr);
                    condition_cfc.parameters.AddElement(ncn);
                    condition = condition_cfc;
                }

                question_colon_expression qce = new question_colon_expression(condition, ncn2, ifnotnull, call_location);

                return qce;
            }