Coal ore can generate below Y=0 when attached to a fossil

Deepslate coal ore doesn't exist, so this may, "Works As Intended".

It should either exist, or coal shouldn't be able to spawn underneath y=0, or at least not 30 blocks down.

Fossils have coal as part of their structure some times.

Due to fossils or potentially other player-defined populators in custom world generation, coal ore can generate below y=0 and as such might need a deepslate variant.

Also as a coal deepslate block would be hard to discern it may need to be replaced with a coal block

Still occurs in worlds generated in 21w08b, added an image. As was said by others, there is no deepslate coal ore so this may just be "works as intended", but just in case.

Ore below y-0 don't have to be deepslate, they are only deepslate if the replace what would have been a deepslate block.
Change log says, "added Deepslate versions of Iron, Gold, Lapis, Redstone, and Diamond ores that generate wherever those ores replace Deepslate"

 Can comfirm, found it too on another world.

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For those saying "but it's not part of world generation, it's part of fossil generation!", that is just a semantic excuse, that fact that it's part of the fossil generation doesn't change anything: ore bellow Y=0 should be deepslate.

One of these solution should "fix" this:

• coal ore need a deepslate variant when the fossil is bellow Y=0

• fossil need to stop generating bellow Y=0 completely

• fossil generating bellow Y=0 don't have any coal

• fossil generating bellow Y=0 have full coal blocks instead of coal ore

There is no reason for keeping fossil bellow Y=0 with stone coal ore, it,s just an oversight the dev forgot about that's all and I'm sure they will fix it in future snapshot for coherence and aesthetics.

Imo this should be fixed by generating coal blocks instead