fixed broken movable TEs under Java 16

src/main/java/carpet/fakes/BlockEntityInterface.java

@@ -0,0 +1,8 @@
+package carpet.fakes;
+
+import net.minecraft.util.math.BlockPos;
+
+public interface BlockEntityInterface
+{
+    void setCMPos(BlockPos pos);
+}

src/main/java/carpet/mixins/BlockEntity_movableBEMixin.java

@@ -1,13 +1,21 @@
 package carpet.mixins;
 
+import carpet.fakes.BlockEntityInterface;
 import net.minecraft.block.entity.BlockEntity;
 import net.minecraft.util.math.BlockPos;
+import org.spongepowered.asm.mixin.Final;
 import org.spongepowered.asm.mixin.Mixin;
-import org.spongepowered.asm.mixin.gen.Accessor;
+import org.spongepowered.asm.mixin.Mutable;
+import org.spongepowered.asm.mixin.Shadow;
 
 @Mixin(BlockEntity.class)
-public interface BlockEntity_movableBEMixin
+public abstract class BlockEntity_movableBEMixin implements BlockEntityInterface
 {
-    @Accessor
-    void setPos(BlockPos pos);
+    @Mutable
+    @Shadow @Final protected BlockPos pos;
+
+    public void setCMPos(BlockPos newPos)
+    {
+        pos = newPos;
+    };
 }

src/main/java/carpet/mixins/PistonBlockEntity_movableTEMixin.java

@@ -1,6 +1,7 @@
 package carpet.mixins;
 
 import carpet.CarpetSettings;
+import carpet.fakes.BlockEntityInterface;
 import carpet.fakes.PistonBlockEntityInterface;
 import carpet.fakes.WorldInterface;
 import net.minecraft.block.Block;
@@ -57,7 +58,7 @@ public abstract class PistonBlockEntity_movableTEMixin extends BlockEntity imple
         this.carriedBlockEntity = blockEntity;
         if (this.carriedBlockEntity != null)
         {
-            ((BlockEntity_movableBEMixin)carriedBlockEntity).setPos(pos);
+            ((BlockEntityInterface)carriedBlockEntity).setCMPos(pos);
             // this might be little dangerous since pos is final for a hashing reason?
             if (world != null) carriedBlockEntity.setWorld(world);
         }