Building Dotty with Eclipse

Build setup

You may need to redo these steps when the build changes.

  1. Run sbt eclipse
  2. In dotty, go to Properties > java build path > Libraries. Remove the Scala Compiler container (currently 2.11.4) and add as an external jar the latest compiler version in the Ivy cache. This is currently:


    But that might change in the future. Or, copy the latest scala compiler from the cache to a stable name and use that as external jar.

  3. It is recommended to change the default output folder (in Properties > java build path > Source) to dotty/classes instead of dotty/bin because dotty/bin is reserved for shell scripts.

If you have CLASSPATH defined:

  1. Update your classpath to contain any new required external libraries to run ./bin/dotc, ./bin/dotr outside of Eclipse.

  2. Open the Run Configurations tab, and edit the tests configuration so that it contains a CLASSPATH variable which reflects the current CLASSPATH.

In order for compilation errors related to ENUM to be resolved, make sure that scala-reflect 2.11.5 is on the classpath.

Running the compiler Main class from Eclipse

  1. Navigate to
  2. Run As... > Scala Application
  3. Run Configurations > Main$ > Classpath > Bootstrap entries:
    • Add the Scala library (Advanced... > Add library... > Scala library)
    • Add the Dotty classfiles (Add projects... > [x] dotty)
  4. Run Configurations > Main$ > Arguments and add ${project_loc}/tests/pos/HelloWorld.scala