```
2021.10.22 07:14:33.963099 [ 3451059 ] {} <Error> Application: DB::Exception: Syntax error (in file ./user_defined/function_a_function.sql): failed at position 39 ('->'): -> ch(2)

$ cat ./user_defined/function_a_function.sql
CREATE FUNCTION a_function AS tuple() -> ch(2)
```
if (!written && 0 == strcmp(name.c_str(), "tupleElement"))
            {
                
                
                
                
                
                
                
                
                
                
                
                
                
                bool tuple_arguments_valid = true;
                const auto * lit_left = arguments->children[0]->as<ASTLiteral>();
                const auto * lit_right = arguments->children[1]->as<ASTLiteral>();
                if (lit_left)
                {
                    Field::Types::Which type = lit_left->value.getType();
                    if (type != Field::Types::Tuple && type != Field::Types::Array)
                    {
                        tuple_arguments_valid = false;
                    }
                }