The bug
Leaves of swamp world generation trees replace all non-full blocks whereas trees place by the world generation in other biome or normally grown trees only replace certain blocks like leaves and vines.
How to reproduce
Seed: 2154973
/tp -13241 69 -3493 -90 20→ ❌ Some fences are missing and instead replaced by leaves
Code analysis
Based on 1.11.2 decompiled using MCP 9.35 rc1
The method net.minecraft.world.gen.feature.WorldGenSwamp.generate(World, Random, BlockPos) starts testing in a 3 block radius for free space starting at position.getY() + 1 + i - 2 but starts placing the leaves at position.getY() - 3 + i.
Attachments
Comments 4
Cannot reproduce for 1.13.1, most likely fixed.
I searched for villages in swamps for around 30 minuts, could not found a single village in a swamp which had leaves around fences.
(ik, one of the screenshots is not in a swamp but thats the best one I found while looking)
Taiga should be fine, therefor I removed that part again.