Paper/paper-server/patches/sources/net/minecraft/network/syncher/SynchedEntityData.java.patch

--- a/net/minecraft/network/syncher/SynchedEntityData.java
+++ b/net/minecraft/network/syncher/SynchedEntityData.java
@@ -51,7 +51,7 @@
     }
 
     private <T> SynchedEntityData.DataItem<T> getItem(EntityDataAccessor<T> key) {
-        return this.itemsById[key.id()];
+        return (SynchedEntityData.DataItem<T>) this.itemsById[key.id()]; // CraftBukkit - decompile error
     }
 
     public <T> T get(EntityDataAccessor<T> data) {
@@ -74,6 +74,13 @@
 
     }
 
+    // CraftBukkit start - add method from above
+    public <T> void markDirty(EntityDataAccessor<T> datawatcherobject) {
+        this.getItem(datawatcherobject).setDirty(true);
+        this.isDirty = true;
+    }
+    // CraftBukkit end
+
     public boolean isDirty() {
         return this.isDirty;
     }
@@ -140,7 +147,7 @@
         if (!Objects.equals(from.serializer(), to.accessor.serializer())) {
             throw new IllegalStateException(String.format(Locale.ROOT, "Invalid entity data item type for field %d on entity %s: old=%s(%s), new=%s(%s)", to.accessor.id(), this.entity, to.value, to.value.getClass(), from.value, from.value.getClass()));
         } else {
-            to.setValue(from.value);
+            to.setValue((T) from.value); // CraftBukkit - decompile error
         }
     }