In Symfony apps, it's possible to use container parameters in the routes config . In Symfony 4.3 we improved this feature to also support boolean parameters, so you can do things like this:

Deprecated Some Router Options¶

The following Routing component config options have been deprecated and they will be removed in Symfony 5.0:

generator_base_class

generator_cache_class

matcher_base_class

matcher_cache_class

These classes are no longer used after some recent changes in the Routing code. Besides, using parameters to define the class to use is a practice that Symfony discouraged a few years ago.