@Override
    public void setStatementOutput(DocumentType documentType, Field field) {
        defaultExp.setStatementOutput(documentType, field);
        for (var expression : cases.values())
            expression.setStatementOutput(documentType, field);
    }
The default expression, or null if none
indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/SwitchExpression.java