Add return types, round 1

Author: nicolas-grekas

Lock.php

@@ -49,7 +49,7 @@ public function __construct(Key $key, PersistingStoreInterface $store, float $tt
         $this->logger = new NullLogger();
     }
 
-    public function __sleep()
+    public function __sleep(): array
     {
         throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
     }

Store/RedisStore.php

@@ -244,12 +244,7 @@ public function exists(Key $key)
         return (bool) $this->evaluate($script, (string) $key, [microtime(true), $this->getUniqueToken($key)]);
     }
 
-    /**
-     * Evaluates a script in the corresponding redis client.
-     *
-     * @return mixed
-     */
-    private function evaluate(string $script, string $resource, array $args)
+    private function evaluate(string $script, string $resource, array $args): mixed
     {
         if (
             $this->redis instanceof \Redis ||