World: change 'closed' to 'unloaded'

this makes more sense overall from a reader's perspective.
and also provide a rug-jerk for any idiots using World->close() when they aren't supposed to? ....

src/world/Position.php

@@ -39,7 +39,7 @@ class Position extends Vector3{
 	 */
 	public function __construct($x, $y, $z, ?World $world){
 		parent::__construct($x, $y, $z);
-		if($world !== null and $world->isClosed()){
+		if($world !== null and !$world->isLoaded()){
 			throw new \InvalidArgumentException("Specified world has been unloaded and cannot be used");
 		}
 
@@ -66,7 +66,7 @@ class Position extends Vector3{
 	 * @throws AssumptionFailedError
 	 */
 	public function getWorld() : World{
-		if($this->world === null || $this->world->isClosed()){
+		if($this->world === null || !$this->world->isLoaded()){
 			throw new AssumptionFailedError("Position world is null or has been unloaded");
 		}
 
@@ -77,7 +77,7 @@ class Position extends Vector3{
 	 * Checks if this object has a valid reference to a loaded world
 	 */
 	public function isValid() : bool{
-		if($this->world !== null and $this->world->isClosed()){
+		if($this->world !== null and !$this->world->isLoaded()){
 			$this->world = null;
 
 			return false;

src/world/World.php

@@ -285,7 +285,7 @@ class World implements ChunkManager{
 	private $generator;
 
 	/** @var bool */
-	private $closed = false;
+	private $unloaded = false;
 	/**
 	 * @var \Closure[]
 	 * @phpstan-var array<int, \Closure() : void>
@@ -493,15 +493,15 @@ class World implements ChunkManager{
 		return $this->worldId;
 	}
 
-	public function isClosed() : bool{
-		return $this->closed;
+	public function isLoaded() : bool{
+		return !$this->unloaded;
 	}
 
 	/**
 	 * @internal
 	 */
-	public function close() : void{
-		if($this->closed){
+	public function onUnload() : void{
+		if($this->unloaded){
 			throw new \InvalidStateException("Tried to close a world which is already closed");
 		}
 
@@ -523,7 +523,7 @@ class World implements ChunkManager{
 		$this->provider = null;
 		$this->blockCache = [];
 
-		$this->closed = true;
+		$this->unloaded = true;
 	}
 
 	/** @phpstan-param \Closure() : void $callback */
@@ -747,7 +747,7 @@ class World implements ChunkManager{
 	 * @internal
 	 */
 	public function doTick(int $currentTick) : void{
-		if($this->closed){
+		if($this->unloaded){
 			throw new \InvalidStateException("Attempted to tick a world which has been closed");
 		}
 
@@ -1046,7 +1046,7 @@ class World implements ChunkManager{
 					 * @phpstan-var array<int, LightArray> $skyLight
 					 * @phpstan-var array<int, int>        $heightMap
 					 */
-					if($this->closed || ($chunk = $this->getChunk($chunkX, $chunkZ)) === null || $chunk->isLightPopulated() === true){
+					if($this->unloaded || ($chunk = $this->getChunk($chunkX, $chunkZ)) === null || $chunk->isLightPopulated() === true){
 						return;
 					}
 					//TODO: calculated light information might not be valid if the terrain changed during light calculation

src/world/WorldManager.php

@@ -168,7 +168,7 @@ class WorldManager{
 		}
 		unset($this->worlds[$world->getId()]);
 
-		$world->close();
+		$world->onUnload();
 		return true;
 	}
 
@@ -321,7 +321,7 @@ class WorldManager{
 	 */
 	public function findEntity(int $entityId) : ?Entity{
 		foreach($this->worlds as $world){
-			assert(!$world->isClosed());
+			assert($world->isLoaded());
 			if(($entity = $world->getEntity($entityId)) instanceof Entity){
 				return $entity;
 			}

src/world/generator/PopulationTask.php

@@ -136,7 +136,7 @@ class PopulationTask extends AsyncTask{
 	public function onCompletion() : void{
 		/** @var World $world */
 		$world = $this->fetchLocal(self::TLS_KEY_WORLD);
-		if(!$world->isClosed()){
+		if($world->isLoaded()){
 			$chunk = $this->chunk !== null ? FastChunkSerializer::deserialize($this->chunk) : null;
 
 			for($i = 0; $i < 9; ++$i){