this is probably not supposed to be like this cause you can place other things like redstone powder, torches, levers, signs and other unsolid blocks on top of them, but not snow-layer-blocks.
way to reproduce:
1. place slab/stair in that way it is upside down.
2. try to place snow-layer-block on it.
3. fail!
(4. rage!!!)??
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Duplicate of MC-2813, please use the search function to see if your bug has already been submitted. Currently over 51% of tickets are being closed as duplicate.
i did, and i could not find anything
Typing "snow slab" into the search field would have yielded MC-2813 as the third result. Do not type overly specific things like "can't place snow-layer-block on top of upside-down slabs and stairs".
i did type exactley that, but i think the reason is that i first searched for that, then i wasted a lot of time on something else, and then i posted it, so i guess the other duplicate was posted right before i posted it... XD