I would like it to be explained, mixins were merged in to master yesterday and I finally think I have ASM figured out.
Found some of what I needed here
The problem it solves is that BlockBreak is a forge event, and because of that it can’t be exposed to the sponge API. But we do have a VoxelEvent in the API. So for the sponge implementation we either need to duplicate the BlockBreak event(by inserting the event posts for VoxelEvent at the correct positions, potentially breaking stuff and separating the forge mods from sponge plugins) or to extend the BreakBlock event so that it functions as a VoxelEvent.
For the other events currently named …
But I still don’t know why that one particular class is modified in that specific place, while the startup and initialization events are injected as part of the EventTransformer class.
The solution for this currently won’t work with Mixins because of this issue:
Both Bukkit and Sponge have chosen to implement damage as a double instead of the default implementation of an float. What this means is that when attempting to create a Mixin for the Player or Entity interfaces, which requires both implementing the Sponge interface and extending the Forge/Minecraft class, that it won’t be possible to implement anything using the Damageable interface.
I may be mistaken and it might be a simple workaround that I’m missing, but I can’t seem to figure it out.
As I am wrapping up finished posts, this was fixed by mixins with the annotations.