Use the latest IntelliJ IDEA release and install the Scala plugin from within the IDE. Compilation withing IDEA is performed in "-Dlocker.skip=1" mode: the sources are built directly using the STARR compiler. The following steps are required to use IntelliJ IDEA on Scala trunk - Run "ant init". This will download some JARs from to ./build/deps, which are included in IntelliJ's classpath. - Run src/intellij/setup.sh - Open ./src/intellij/scala-lang.ipr in IntelliJ - File, Project Settings, Project, SDK. Create an SDK entry named "1.6" containing the java 1.6 SDK