I cloned a chest right beside another chest without a blocks space.
What happened was the first chest went invisible, but was still there. Right clicking any of the chests (not the invisible one) will display the inventory from all of the chests.
How I did this:
1. Created a large chest.
2. Used the new clone command to clone the chest right beside itself using relative coordinates. (clone ~ ~ ~-1 ~-1 ~ ~-1 ~-3 ~ ~-1)
3. Ran the command.
This can also be done with setblock, and most likely fill aswell.
Note: Breaking the second chest will return the first to normal.
Another Note: One thing I noticed since I originally posted this is that right clicking the invisible chest shows a double chest inventory like normal.