playframework/Play20 — comment on commit 2956aaa4306db3df7ef2036ba41237387097cd5a
File: framework/play/src/main/scala/play/api/mvc/Results.scala line 259
By julienrf:

Why isn’t this trait sealed?
It may help you to forget to match against a ContentTypeOf subclass in the pattern matching statement [below](https://github.com/playframework/Play20/commit/2956aaa4306db3df7ef2036ba41237387097cd5a#L1R332)