use Config;

class Test
{
 public function index()
 {
 return Config::get('app.name');
 }
}

public function bootstrap(Application $app)
{
 Facade::clearResolvedInstances();
 Facade::setFacadeApplication($app);

 AliasLoader::getInstance(array_merge(
 $app->make('config')->get('app.aliases', []),
 $app->make(PackageManifest::class)->aliases()
 ))->register();
}

 "App" => "Illuminate\Support\Facades\App"
 "Artisan" => "Illuminate\Support\Facades\Artisan"
 "Auth" => "Illuminate\Support\Facades\Auth"
 "Blade" => "Illuminate\Support\Facades\Blade"
 ...

 /**
 * Prepend the load method to the auto-loader stack.
 *
 * @return void
 */
 protected function register()
 {
 if (! $this->registered) {
  spl_autoload_register([$this, 'load'], true, true);

  $this->registered = true;
 }
 }

<?php

use Config;
use App\User;

class Test
{
 public function index()
 {
 Config::get('app.name');
 new User();
 }
}

public function load($alias)
{
 if (isset($this->aliases[$alias])) {
 return class_alias($this->aliases[$alias], $alias);
 }
}

class foo { }

class_alias('foo', 'bar');

$a = new foo;
$b = new bar;

// the objects are the same
var_dump($a == $b, $a === $b); //true
var_dump($a instanceof $b); //false

// the classes are the same
var_dump($a instanceof foo); //true
var_dump($a instanceof bar); //true

var_dump($b instanceof foo); //true
var_dump($b instanceof bar); //true

<?php

use Config;

class Test
{
 public function index()
 {
 Config::get('app.name');
 }
}

<?php

use Illuminate\Support\Facades\Config;

class Test
{
 public function index()
 {
  Config::get('app.name');
 }
}

<?php

public static function __callStatic($method, $args)
{
 $instance = static::getFacadeRoot();

 if (! $instance) {
  throw new RuntimeException('A facade root has not been set.');
 }

 return $instance->$method(...$args);
}

protected static function getFacadeAccessor()
{
 return 'config';
} 

public static function getFacadeRoot()
{
 $name = static::getFacadeAccessor();
 
 if (is_object($name)) {
  return $name;
 }

 if (isset(static::$resolvedInstance[$name])) {
  return static::$resolvedInstance[$name];
 }

 return static::$resolvedInstance[$name] = static::$app[$name];
}

<?php
//Illuminate\Foundation\Bootstrap/LoadConfiguration

$app->instance('config', $config = new Repository($items));