This is a summary of the steps to upgrade from Xtext 2.3 to 2.4:
- The plugin org.eclipse.xtext.xtend2.lib has been renamed to org.eclipse.xtend2.lib
- In the *.mwe2 file of your DSL, replace EcoreGeneratorFragment with EMFGeneratorFragment
- Run the *.mwe2 script to regenerate the whole project
- Merge plugin.xml_gen and plugin.xml