**Use case**
`SELECT POSITION('/' IN s) FROM (SELECT 'Hello/World' AS s);`

The same as `position(s, '/')`

&& contents_begin[2] >= '0' && contents_begin[2] <= '9'
        && contents_begin[3] >= '0' && contents_begin[3] <= '9'
        && contents_begin[4] == '-'
        && contents_begin[5] >= '0' && contents_begin[5] <= '9'
        && contents_begin[6] >= '0' && contents_begin[6] <= '9'
        && contents_begin[7] == '-'
        && contents_begin[8] >= '0' && contents_begin[8] <= '9'
        && contents_begin[9] >= '0' && contents_begin[9] <= '9')
    {
        std::string contents_str(contents_begin, contents_end - contents_begin);
        throw Exception("Argument of function toDate is unquoted: toDate(" + contents_str + "), must be: toDate('" + contents_str + "')"
            , ErrorCodes::SYNTAX_ERROR);
    }
    
    if (allow_function_parameters && pos->type == TokenType::OpeningRoundBracket)
    {
        ++pos;
        
        if (has_distinct_modifier)
            return false;
        expr_list_params = expr_list_args;
        expr_list_args = nullptr;
        if (distinct.ignore(pos, expected))
            has_distinct_modifier = true;
        if (!contents.parse(pos, expr_list_args, expected))
            return false;
        if (pos->type != TokenType::ClosingRoundBracket)
            return false;
        ++pos;
    }