In case of:

services: service_name: class: Some\Class\Here arguments: [@request]

ScopeWideningInjectionException probably will be throw, and as described in this exception message:

(...) In rare, special cases however that might not be necessary, then you can set the reference to strict=false to get rid of this error.

In case of xml or php it's simple, but when it comes to yaml it looks like:

services: service_name: class: Some\Class\Here arguments: [@request=]