[5.0] Add return types on internal|final|private methods

Author: nicolas-grekas

Crawler.php

@@ -898,7 +898,7 @@ public static function xpathLiteral(string $s)
      *
      * @return static
      */
-    private function filterRelativeXPath(string $xpath)
+    private function filterRelativeXPath(string $xpath): object
     {
         $prefixes = $this->findNamespacePrefixes($xpath);
 
@@ -1140,7 +1140,7 @@ private function findNamespacePrefixes(string $xpath): array
      *
      * @return static
      */
-    private function createSubCrawler($nodes)
+    private function createSubCrawler($nodes): object
     {
         $crawler = new static($nodes, $this->uri, $this->baseHref);
         $crawler->isHtml = $this->isHtml;