I'm using IntelliJ 12.1.6 with the latest Ruby plugin, and I installed Ruby 2.1.0 (ruby 2.1.0p0 (2013-12-25 revision 44422) [x86_64-darwin13.0]) on my Mac with the latest version of rbenv. In IntelliJ the language level is set as 1.8 and greyed out in Platform Settings > SDKs, so I can't change it.
I've read one or two other discussions about similar problems, but it's not clear what the cause is or how to solve the problem. I've tried re-adding the SDK, and reinstalling Ruby 2.1.0 again. Homebrew, rbenv, ruby-build etc are all up-to-date.
Does anybody have any idea how the language level is automatically selected? I can see that IntelliJ is including the folder rubystubs18 in the classpath.