Fix WorldEditPlugin assuming that worlds are an instance of BukkitWorld.

Fixes WORLDEDIT-3168.

src/bukkit/java/com/sk89q/worldedit/bukkit/BukkitAdapter.java

@@ -35,6 +35,27 @@ final class BukkitAdapter {
     private BukkitAdapter() {
     }
 
+    /**
+     * Convert any WorldEdit world into an equivalent wrapped Bukkit world.
+     *
+     * <p>If a matching world cannot be found, a {@link RuntimeException}
+     * will be thrown.</p>
+     *
+     * @param world the world
+     * @return a wrapped Bukkit world
+     */
+    public static BukkitWorld asBukkitWorld(World world) {
+        if (world instanceof BukkitWorld) {
+            return (BukkitWorld) world;
+        } else {
+            BukkitWorld bukkitWorld = WorldEditPlugin.getInstance().getInternalPlatform().matchWorld(world);
+            if (bukkitWorld == null) {
+                throw new RuntimeException("World '" + world.getName() + "' has no matching version in Bukkit");
+            }
+            return bukkitWorld;
+        }
+    }
+
     /**
      * Create a WorldEdit world from a Bukkit world.
      *

src/bukkit/java/com/sk89q/worldedit/bukkit/BukkitServerInterface.java

@@ -110,9 +110,9 @@ public class BukkitServerInterface extends ServerInterface implements MultiUserP
 
     @Nullable
     @Override
-    public com.sk89q.worldedit.world.World matchWorld(com.sk89q.worldedit.world.World world) {
+    public BukkitWorld matchWorld(com.sk89q.worldedit.world.World world) {
         if (world instanceof BukkitWorld) {
-            return world;
+            return (BukkitWorld) world;
         } else {
             World bukkitWorld = server.getWorld(world.getName());
             return bukkitWorld != null ? new BukkitWorld(bukkitWorld) : null;

src/bukkit/java/com/sk89q/worldedit/bukkit/WorldEditPlugin.java

@@ -412,7 +412,7 @@ public class WorldEditPlugin extends JavaPlugin implements TabCompleter {
 
         try {
             Region region = selector.getRegion();
-            World world = ((BukkitWorld) session.getSelectionWorld()).getWorld();
+            World world = BukkitAdapter.asBukkitWorld(session.getSelectionWorld()).getWorld();
 
             if (region instanceof CuboidRegion) {
                 return new CuboidSelection(world, selector, (CuboidRegion) region);