[MC-190769] Oak trees grow too close to build limit causing missing top leaves layer

The bug

Oak (and maybe even all trees) can grow one block too close to the built limit y=256 causing their top leaves layer to be missing.

Reproduction steps

Create a superflat world with the following preset

251*minecraft:air,minecraft:dirt,minecraft:oak_sapling;minecraft:the_void

Teleport to the surface
```
/teleport ~ 256 ~
```
Wait some time
❌ Oak trees without top leaves layer grow

Linked issues

relates to 1

MC-117805 Oak trees can generate right below height limit (y = 256) resulting in incomplete tree Resolved

Attachments

Comments 3

migrated 2020-06-21T10:10:16Z

Can confirm for 1.15.2

[Mod] violine1101 2020-06-21T10:49:23Z

The ticket for 1.15.2 is MC-117805.

gaspoweredpick 2020-06-22T18:19:44Z

I would argue it's actually two blocks, as it causes snow layers to be cut off at height limit, even when the trees themselves generate "as expected". The reason I deemed MC-117805 as fixed is because even if it generated "as expected", it would still cut off snow layers. I think snow layers getting cut off via a particular structure/decoration, and said structure/decoration itself getting cut off, is the same issue.