URL link redirect Drupal8

• l()Is gone. Use \drupal\core\link for full link objects,--link object
  and \drupal\core\url for URL generation. ---generate URLs
• drupal_goto()Is gone.  Use a redirectresponse, or the redirect () method in your controller. --Jump
• ------------------https://dev.acquia.com/blog/generating-urls-and-redirects-in-drupal-8/22/02/2016/9626

Remember the previous time on drupal/core/url->tostring (true| FALSE) also tangled half a day
Actually, the documentation is very clear.
That is, if true, that returns an object, and many times we just need a string.

* @return String|\drupal\core\generatedurl
* A string URL.
* When $collect _bubbleable_metadata are TRUE, a Generatedurl object is
* Returned, containing the generated URL plus bubbleable metadata.

URL link redirect Drupal8