How do I check if a user may access a given route?
I don't know why 


$_url = Url::fromRoute('', [], ['language' => $language]);


Doesn't work with route name &lt;current&gt; but it works with other route names.
For example with route with name some_module.some_route_name the following 
will work. 



  $language = \Drupal::languageManager()->getCurrentLanguage()->getId();
  $_url = Url::fromRoute('some_module.some_route_name', [], ['language' => $language]);
  $userCurrent = \Drupal::currentUser();
  if ($_url->access($userCurrent)) {
    //- Do Stuff
  }



In your case for the current route. Try this out.


use Drupal\Core\Url;

  $request = \Drupal::request();
  $_url = Url::createFromRequest($request);
  $userCurrent = \Drupal::currentUser();
   if ($_url->access($userCurrent)) {
     //- Do Stuff 
  }