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 FunctionPtr create() { return std::make_shared<FunctionConvert>(); }
    String getName() const override
    {
        return name;
    }
    bool isVariadic() const override { return true; }
    size_t getNumberOfArguments() const override { return 0; }
    bool isInjective(const ColumnsWithTypeAndName &) const override { return std::is_same_v<Name, NameToString>; }
    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & arguments) const override
    {
        
        return !(to_date_or_datetime && isNumber(*arguments[0].type));
    }
    using DefaultReturnTypeGetter = std::function<DataTypePtr(const ColumnsWithTypeAndName &)>;
    static DataTypePtr getReturnTypeDefaultImplementationForNulls(const ColumnsWithTypeAndName & arguments, const DefaultReturnTypeGetter & getter)
    {
        NullPresence null_presence = getNullPresense(arguments);
        if (null_presence.has_null_constant)
        {
            return makeNullable(std::make_shared<DataTypeNothing>());
        }
        if (null_presence.has_nullable)
        {
            auto nested_columns = Block(createBlockWithNestedColumns(arguments));
            auto return_type = getter(ColumnsWithTypeAndName(nested_columns.begin(), nested_columns.end()));
            return makeNullable(return_type);
        }
        return getter(arguments);
    }
    DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override