I am trying to assign the result of the following instanceof pattern matching switch to the variable languageCodeOfReturnValue.

    String languageCodeOfReturnValue = switch (object){
                case PlantGuidePageWrapperDTO plantGuidePageWrapperDTO -> plantGuidePageWrapperDTO.getSeedDetailsDTO().getPageSummaryLanguageCode();
                case JournalEntryDetailsDTO journalEntryDetailsDTO -> journalEntryDetailsDTO.getLanguageCode();
                case JournalOverviewDTO journalOverviewDTO -> journalOverviewDTO.getPageSummaryLanguageCode();
                default -> null;
    };

But this code causes the following warning:

Value 'switch (object){ case PlantGuidePageWrapperDTO plantGuidePageWrapperDTO -> plant...' is always 'null'

When i remove the default clause the warning disappears but then i'm left with a syntax error because then the switch doesn't cover all possible values. The warning disappears when i replace null with and empty string ''. However i really want the default value to be null.

So my question is twofold: First, why is the switch statement result always null when i return a null value in the default case. And second, What then is the proper way to return a null value when none of the patterns match?

Thank you

EDIT: I am using Intellij IDEA as IDE. Perhaps its an inellij IDEA bug?