millhouse’s answer helped me find the right answer. Play 2.2 (and perhaps earlier versions, haven’t checked) output a scala version of the routes file to project_dir/target/scala-2.10/src_managed/main So for IntelliJ to get the highlighting right you need to make sure that src_managed/main is added as a source folder. The reverse routes for javascript are for some reason included in project_dir/target/scala-2.10/classes_managed so you’ll have to add that as well. (In your screenshot it looks like classes_managed is set to excluded so you’ll want to un-exclude it by pressing the x button on the right hand side.)
Here’s a screen shot of my project structure:
Update:
In Play 2.3 (or perhaps recent versions of IntelliJ) adding the classes_managed no longer fixes the problem. Instead of adding classes_managed to the project’s sources add it to it’s dependencies. By doing that IntelliJ should be able to pick up the compiled routes.class.
