@SuppressWarnings("unchecked")
    public static <D> Expression<D> getAny(D arg) {
        Object current = aliasFactory.getCurrentAndReset();
        if (arg instanceof ManagedObject) {
            return (Expression<D>) ((ManagedObject) arg).__mappedPath();
        } else if (current != null) {
            return (Expression<D>) current;
        } else {
            throw new IllegalArgumentException("No path mapped to " + arg);
        }
    }
Convert the given alias to an expression

@param <D>
@param arg alias instance
@return underlying expression
querydsl-core/src/main/java/com/querydsl/core/alias/Alias.java