https://speakerdeck.com/gwengrid/keep-calm-and-type-erase-on
Step-By-Step, writing a type-erased wrapper class by Hector Matos
Why?! No type parameters on generic protocols pt 1 pt 2 by Russ Bishop
Why?! No covariance for generic protocols by Mike Ash
A nice, contained dummy example by Ray Fix
A bigger example of type-erasure by Kazunobu Tasaka
An even bigger, production-level use of type-erasure by Benjamin Encz