Since 2008 my generics projects have not compiled in IDEA and also in ANT script running under IDEA.
To enable generics compilation back, you need follow changes:
1. Add to your 'generics' library also gjc-rt.jar. Be sure that this jar is above JDK.
2. In compiler settings put to Additional compiler args follow line: -bootclasspath $APPLICATION_HOME_DIR$/lib/generics/collect.jar. Restart IDEA.
3. Check project compilation by Ctrl+F9 and Generics code editing.
4. You also need make some changes in ANT task for generics: