protected Item positiveItem() {
        int position = tokens.getPosition();
        Item item = null;

        try {
            if ( ! tokens.skipMultiple(PLUS)) {
                return null;
            }

            if (tokens.currentIsNoIgnore(SPACE)) {
                return null;
            }

            item = indexableItem("").getFirst();

            if (item == null) {
                item = compositeItem();
            }
            if (item!=null)
                item.setProtected(true);
            return item;
        } finally {
            if (item == null) {
                tokens.setPosition(position);
            }
        }
    }
Removes and returns the first <i>not</i> found in the composite, or returns null if there's none
container-search/src/main/java/com/yahoo/prelude/query/parser/SimpleParser.java