phpstan: enable checkMissingCallableSignature

src/pocketmine/plugin/PluginManager.php

@@ -701,6 +701,7 @@ class PluginManager{
 				}
 
 				$handlerClosure = $method->getClosure($listener);
+				if($handlerClosure === null) throw new AssumptionFailedError("This should never happen");
 
 				try{
 					$paramType = $parameters[0]->getType();

src/pocketmine/utils/Utils.php

@@ -117,6 +117,8 @@ class Utils{
 	/**
 	 * Generates an unique identifier to a callable
 	 *
+	 * @phpstan-param callable(mixed...) : mixed $variable
+	 *
 	 * @return string
 	 */
 	public static function getCallableIdentifier(callable $variable){
@@ -132,6 +134,7 @@ class Utils{
 	/**
 	 * Returns a readable identifier for the given Closure, including file and line.
 	 *
+	 * @phpstan-param \Closure(mixed...) : mixed $closure
 	 * @throws \ReflectionException
 	 */
 	public static function getNiceClosureName(\Closure $closure) : string{
@@ -685,6 +688,8 @@ class Utils{
 	 *
 	 * @param callable $signature Dummy callable with the required parameters and return type
 	 * @param callable $subject Callable to check the signature of
+	 * @phpstan-param callable(mixed...) : mixed $signature
+	 * @phpstan-param callable(mixed...) : mixed $subject
 	 *
 	 * @throws \DaveRandom\CallbackValidator\InvalidCallbackException
 	 * @throws \TypeError