Revert [Core] No need reindex FileWithoutNamespace on beforeTraverse (#…

…4043) (#4044)

This reverts commit 90b1f9f.

src/Rector/AbstractRector.php

@@ -186,7 +186,11 @@ public function beforeTraverse(array $nodes): ?array
             if (! $childStmt instanceof FileWithoutNamespace) {
                 $childStmt->setAttribute(AttributeKey::STMT_KEY, $key);
                 continue;
-            }   
+            }
+
+            foreach ($childStmt->stmts as $keyChildStmt => $childStmtStmt) {
+                $childStmtStmt->setAttribute(AttributeKey::STMT_KEY, $keyChildStmt);
+            }
         }
 
         return parent::beforeTraverse($nodes);