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?
const auto nested_function = prepareUnpackDictionaries(from_nested_type, to_nested_type);
        return [nested_function, from_nested_type, to_nested_type](
                ColumnsWithTypeAndName & arguments, const DataTypePtr &, const ColumnNullable * nullable_source, size_t ) -> ColumnPtr
        {
            const auto & argument_column = arguments.front();
            const ColumnArray * col_array = nullptr;
            if (const ColumnMap * col_map = checkAndGetColumn<ColumnMap>(argument_column.column.get()))
                col_array = &col_map->getNestedColumn();
            else
                col_array = checkAndGetColumn<ColumnArray>(argument_column.column.get());
            if (col_array)
            {
                
                ColumnsWithTypeAndName nested_columns{{ col_array->getDataPtr(), from_nested_type, "" }};
                
                auto result_column = nested_function(nested_columns, to_nested_type, nullable_source, nested_columns.front().column->size());
                
                return ColumnArray::create(result_column, col_array->getOffsetsPtr());
            }
            else
            {
                throw Exception(ErrorCodes::LOGICAL_ERROR,
                    "Illegal column {} for function CAST AS Array",
                    argument_column.column->getName());
            }
        };
    }
    using ElementWrappers = std::vector<WrapperType>;
    ElementWrappers getElementWrappers(const DataTypes & from_element_types, const DataTypes & to_element_types) const