Fix issue with checking nullable return statements.

Author: Sergei Filonich

src/Check/ReturnCheck.php

@@ -49,7 +49,7 @@ public function check(FileInfo $file)
                 if ($method['docblock']['return'] !== $method['return']) {
                     if ($method['return'] === 'array' && substr($method['docblock']['return'], -2) === '[]') {
                         // Do nothing because this is fine.
-                    } else {
+                    } elseif (!is_array($method['return']) || !$this->checkMultipleReturnStatements($method)) {
                         $this->fileStatus->add(
                             new ReturnMismatchWarning(
                                 $file->getFileName(),
@@ -73,4 +73,16 @@ public function enabled()
     {
         return !$this->config->isSkipSignatures();
     }
+
+    /**
+     * @param array $method
+     * @return bool
+     */
+    private function checkMultipleReturnStatements(array $method): bool
+    {
+        $dockReturn = explode('|', $method['docblock']['return']);
+        $methodReturn = $method['return'];
+
+        return count(array_diff($dockReturn, $methodReturn)) == 0 && count(array_diff($methodReturn, $dockReturn)) == 0;
+    }
 }