fabpot/Twig — comment on commit 865a7039f8f93e0ad9e76c129481a0bbf9259aa3
File: lib/Twig/Environment.php line 108
By stof:

I think the way it works in ``Twig_Extensions_Extension_Debug`` is better as it makes the tag a no-op in non-debug mode instead of removing it. The current implementation means that your template will be broken when switching off the debug mode if you forgot to remove a dump statement.

Btw, I find it funny to see it back in the core when it was moved to the extension repo just before the stable release :)