```
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)
```
#include <Parsers/ASTFunction.h>
#include <Common/quoteString.h>
#include <Common/FieldVisitorToString.h>
#include <Common/SipHash.h>
#include <Common/typeid_cast.h>
#include <DataTypes/IDataType.h>
#include <DataTypes/NumberTraits.h>
#include <IO/Operators.h>
#include <IO/WriteBufferFromString.h>
#include <IO/WriteHelpers.h>
#include <Parsers/ASTExpressionList.h>
#include <Parsers/ASTIdentifier.h>
#include <Parsers/ASTLiteral.h>
#include <Parsers/ASTSubquery.h>
#include <Parsers/ASTWithAlias.h>
#include <Parsers/queryToString.h>
namespace DB
{
namespace ErrorCodes
{
    extern const int UNEXPECTED_EXPRESSION;
    extern const int UNEXPECTED_AST_STRUCTURE;
}
void ASTFunction::appendColumnNameImpl(WriteBuffer & ostr) const