Currently, the UI for compiler switching within Groovy-Eclipse (M1) is still experimental. If you cannot switch compilers from the Groovy Compiler preference page, follow the instructions to perform the switch manually:
- Shut down Eclipse
- Go to eclipse/configuration/org.eclipse.equinox.simpleconfigurator
- Make a backup copy of bundles.info
- Open bundles.info in a text editor
- Find the line for org.codehaus.groovy_1.7.0 and delete
- Restart eclipse
To re-enable the 1.7 compiler, simply reinstate the backed up copy of bundles.info.