[8.x] Add forwardDecoratedCallTo (laravel#38800)

* [8.x] Add forwardDecoratedCallTo

* Code style

* Update ForwardsCalls.php

Co-authored-by: Taylor Otwell <taylor@laravel.com>

src/Illuminate/Database/Eloquent/Relations/Relation.php

@@ -489,13 +489,7 @@ public function __call($method, $parameters)
             return $this->macroCall($method, $parameters);
         }
 
-        $result = $this->forwardCallTo($this->query, $method, $parameters);
-
-        if ($result === $this->query) {
-            return $this;
-        }
-
-        return $result;
+        return $this->forwardDecoratedCallTo($this->query, $method, $parameters);
     }
 
     /**

src/Illuminate/Support/Traits/ForwardsCalls.php

@@ -41,6 +41,27 @@ protected function forwardCallTo($object, $method, $parameters)
         }
     }
 
+    /**
+     * Forward a method call to the given object, returning $this if the forwarded call returned itself.
+     *
+     * @param  mixed  $object
+     * @param  string  $method
+     * @param  array  $parameters
+     * @return mixed
+     *
+     * @throws \BadMethodCallException
+     */
+    protected function forwardDecoratedCallTo($object, $method, $parameters)
+    {
+        $result = $this->forwardCallTo($object, $method, $parameters);
+
+        if ($result === $object) {
+            return $this;
+        }
+
+        return $result;
+    }
+
     /**
      * Throw a bad method call exception for the given method.
      *