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?
{
        
        if (checkAndGetDataType<DataTypeString>(from_type_untyped.get()))
        {
            return &ConvertImplGenericFromString<ColumnString>::execute;
        }
        const auto * from_type = checkAndGetDataType<DataTypeArray>(from_type_untyped.get());
        const auto * from_type_map = checkAndGetDataType<DataTypeMap>(from_type_untyped.get());
        
        if (from_type_map)
            from_type = checkAndGetDataType<DataTypeArray>(from_type_map->getNestedType().get());
        if (!from_type)
        {
            throw Exception(ErrorCodes::TYPE_MISMATCH,
                "CAST AS Array can only be performed between same-dimensional Array, Map or String types");
        }
        DataTypePtr from_nested_type = from_type->getNestedType();
        
        bool from_empty_array = isNothing(from_nested_type);
        if (from_type->getNumberOfDimensions() != to_type.getNumberOfDimensions() && !from_empty_array)
            throw Exception(ErrorCodes::TYPE_MISMATCH,
                "CAST AS Array can only be performed between same-dimensional array types");
        const DataTypePtr & to_nested_type = to_type.getNestedType();