I am exploring the Cats in IntelliJ, but despite the IntelliJ Scala plugin's support for the Kind Projector plugin, IntelliJ fails to recognize the plugin's type lambda notation (λ). Is there a trick to enabling this? I don't see Kind Projector listed after running code inspections, although Kind Projector inspection options are available and enabled in preferences. My IntelliJ version is 2016.2.2 and Scala plugin version 2016.2.1.
As of this writing, and with v2016.3.1 EAP, IDEA Scala plugin doesn't support polymorphic lambdas. If you scroll down to the comments on the page you referred to, you'll see that someone requested for that feature.