How to use Scala in IntelliJ IDEA (or: why is it so difficult to get a working IDE for Scala)?

Question

I recently gave up trying to use Scala in Eclipse (basic stuff like completion doesn\'t work). So now I\'m trying IntelliJ. I\'m not getting very far.

I\'ve been able to

Answer 1

I was getting this error and also had to right click on the project and "Open Module Settings". However, it was more than just hitting apply. I had to make sure that my Content Root was correct for each project. For some reason, there were some incorrect Source and Test Folders.

My project uses maven as the main build tool and importing the project into Intellij is probably what created these incorrect settings.