I expect it should work:
```
:) select CAST(CAST('{"x" : 1}', 'Object(\'json\')'), 'Object(Nullable(\'json\'))')

SELECT CAST(CAST('{"x" : 1}', 'Object(\'json\')'), 'Object(Nullable(\'json\'))')

Query id: fb057b45-b72a-4d22-9b38-a3136cdf2465


0 rows in set. Elapsed: 0.002 sec.

Received exception from server (version 22.5.1):
Code: 53. DB::Exception: Received from localhost:9000. DB::Exception: Cast to Object can be performed only from flatten named Tuple, Map or String. Got: Object('json'): While processing CAST(CAST('{"x" : 1}', 'Object(\'json\')'), 'Object(Nullable(\'json\'))'). (TYPE_MISMATCH)
```

@CurtizJ what do you think?
{
        static constexpr bool throw_exception = std::is_same_v<ReturnType, void>;
        if constexpr (throw_exception)
        {
            writeString(type->getNameForValue(x), wb);
        }
        else
        {
            StringRef res;
            bool is_ok = type->getNameForValue(x, res);
            if (is_ok)
                writeString(res, wb);
            return ReturnType(is_ok);
        }
    }
};
template <typename FieldType>
struct FormatImpl<DataTypeDecimal<FieldType>>
{
    template <typename ReturnType = void>
    static ReturnType execute(const FieldType x, WriteBuffer & wb, const DataTypeDecimal<FieldType> * type, const DateLUTImpl *)