Using the nightly build, I'm seeing lots of these:

java.lang.ArrayIndexOutOfBoundsException: -1
at scala.collection.mutable.WrappedArray$ofChar.apply(WrappedArray.scala:123)
at scala.collection.mutable.WrappedArray$ofChar.apply(WrappedArray.scala:120)
at scala.tools.eclipse.ScalaWordFinder$.find$1(ScalaWordFinder.scala:52)
at scala.tools.eclipse.ScalaWordFinder$.findWord(ScalaWordFinder.scala:72)
at scala.tools.eclipse.javaelements.ScalaSelectionEngine$$anonfun$select$1.apply(ScalaSelectionEngine.scala:55)
at scala.tools.eclipse.javaelements.ScalaSelectionEngine$$anonfun$select$1.apply(ScalaSelectionEngine.scala:44)
at scala.tools.eclipse.util.Cached$$anonfun$apply$1.apply(Cached.scala:21)
at scala.tools.eclipse.util.Cached$$anonfun$apply$1.apply(Cached.scala:21)
at scala.tools.eclipse.util.Cached$class.locked(Cached.scala:83)
at scala.tools.eclipse.util.Cached$class.apply(Cached.scala:20)
at scala.tools.eclipse.ScalaPresentationCompiler$CachedCompilerResult.apply(ScalaPresentationCompiler.scala:67)
at scala.tools.eclipse.ScalaPresentationCompiler.withCompilerResult(ScalaPresentationCompiler.scala:90)
at scala.tools.eclipse.ScalaProject$$anonfun$withCompilerResult$1.apply(ScalaProject.scala:369)
at scala.tools.eclipse.ScalaProject$$anonfun$withCompilerResult$1.apply(ScalaProject.scala:368)
at scala.tools.eclipse.util.Cached$$anonfun$apply$1.apply(Cached.scala:21)
at scala.tools.eclipse.util.Cached$$anonfun$apply$1.apply(Cached.scala:21)
at scala.tools.eclipse.util.Cached$class.locked(Cached.scala:83)
at scala.tools.eclipse.util.Cached$class.apply(Cached.scala:20)
at scala.tools.eclipse.ScalaProject$$anon$1.apply(ScalaProject.scala:39)
at scala.tools.eclipse.ScalaProject.withPresentationCompiler(ScalaProject.scala:364)
at scala.tools.eclipse.ScalaProject.withCompilerResult(ScalaProject.scala:368)
at scala.tools.eclipse.javaelements.ScalaCompilationUnit$$anonfun$withCompilerResult$1.apply(ScalaCompilationUnit.scala:49)
at scala.tools.eclipse.javaelements.ScalaCompilationUnit$class.withDocument(ScalaCompilationUnit.scala:41)
at scala.tools.eclipse.javaelements.ScalaSourceFile.withDocument(ScalaSourceFile.scala:40)
at scala.tools.eclipse.javaelements.ScalaCompilationUnit$class.withCompilerResult(ScalaCompilationUnit.scala:49)
at scala.tools.eclipse.javaelements.ScalaSourceFile.withCompilerResult(ScalaSourceFile.scala:40)
at scala.tools.eclipse.javaelements.ScalaSelectionEngine.select(ScalaSelectionEngine.scala:44)
at scala.tools.eclipse.javaelements.ScalaCompilationUnit$class.codeSelect(ScalaCompilationUnit.scala:148)
at scala.tools.eclipse.javaelements.ScalaSourceFile.codeSelect(ScalaSourceFile.scala:40)
at scala.tools.eclipse.javaelements.ScalaSourceFile.codeSelect(ScalaSourceFile.scala:70)
at org.eclipse.jdt.internal.core.CompilationUnit.codeSelect(CompilationUnit.java:371)
at org.eclipse.jdt.internal.ui.actions.SelectionConverter.codeResolve(SelectionConverter.java:256)
at org.eclipse.jdt.internal.ui.actions.SelectionConverter.codeResolve(SelectionConverter.java:144)
at org.eclipse.jdt.internal.ui.actions.SelectionConverter.codeResolve(SelectionConverter.java:129)
at org.eclipse.jdt.internal.ui.actions.SelectionConverter.getStructuredSelection(SelectionConverter.java:75)
at org.eclipse.jdt.internal.ui.util.JavaUIHelp.getHelpContextProvider(JavaUIHelp.java:60)
at org.eclipse.jdt.internal.ui.javaeditor.JavaEditor.getAdapter(JavaEditor.java:2196)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitEditor.getAdapter(CompilationUnitEditor.java:1743)
at org.eclipse.help.ui.internal.views.HelpView.handlePartActivation(HelpView.java:124)
at org.eclipse.help.ui.internal.views.HelpView.partActivated(HelpView.java:213)
at org.eclipse.ui.internal.PartListenerList2$1.run(PartListenerList2.java:70)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.runtime.Platform.run(Platform.java:888)
at org.eclipse.ui.internal.PartListenerList2.fireEvent(PartListenerList2.java:55)
at org.eclipse.ui.internal.PartListenerList2.firePartActivated(PartListenerList2.java:68)
at org.eclipse.ui.internal.PartService.firePartActivated(PartService.java:192)
at org.eclipse.ui.internal.PartService.setActivePart(PartService.java:306)
at org.eclipse.ui.internal.WWinPartService.updateActivePart(WWinPartService.java:131)
at org.eclipse.ui.internal.WWinPartService.access$0(WWinPartService.java:122)
at org.eclipse.ui.internal.WWinPartService$WWinListener.partDeactivated(WWinPartService.java:50)
at org.eclipse.ui.internal.PartListenerList2$4.run(PartListenerList2.java:115)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.runtime.Platform.run(Platform.java:888)
at org.eclipse.ui.internal.PartListenerList2.fireEvent(PartListenerList2.java:55)
at org.eclipse.ui.internal.PartListenerList2.firePartDeactivated(PartListenerList2.java:113)
at org.eclipse.ui.internal.PartService.firePartDeactivated(PartService.java:242)
at org.eclipse.ui.internal.PartService.setActivePart(PartService.java:300)
at org.eclipse.ui.internal.WorkbenchPagePartList.fireActivePartChanged(WorkbenchPagePartList.java:57)
at org.eclipse.ui.internal.PartList.setActivePart(PartList.java:136)
at org.eclipse.ui.internal.WorkbenchPage.setActivePart(WorkbenchPage.java:3531)
at org.eclipse.ui.internal.WorkbenchPage.activate(WorkbenchPage.java:614)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditorBatched(WorkbenchPage.java:2869)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditor(WorkbenchPage.java:2762)
at org.eclipse.ui.internal.WorkbenchPage.access$11(WorkbenchPage.java:2754)
at org.eclipse.ui.internal.WorkbenchPage$10.run(WorkbenchPage.java:2705)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2701)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2685)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2676)
at org.eclipse.search.internal.ui.text.EditorOpener.showWithReuse(EditorOpener.java:116)
at org.eclipse.search.internal.ui.text.EditorOpener.openAndSelect(EditorOpener.java:58)
at org.eclipse.search.internal.ui.text.FileSearchPage.showMatch(FileSearchPage.java:172)
at org.eclipse.search.ui.text.AbstractTextSearchViewPage$7.run(AbstractTextSearchViewPage.java:884)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.search.ui.text.AbstractTextSearchViewPage.showMatch(AbstractTextSearchViewPage.java:887)
at org.eclipse.search.ui.text.AbstractTextSearchViewPage.showCurrentMatch(AbstractTextSearchViewPage.java:952)
at org.eclipse.search.ui.text.AbstractTextSearchViewPage.gotoNextMatch(AbstractTextSearchViewPage.java:917)
at org.eclipse.search.ui.text.AbstractTextSearchViewPage.handleOpen(AbstractTextSearchViewPage.java:1376)
at org.eclipse.search.internal.ui.text.FileSearchPage.handleOpen(FileSearchPage.java:192)
at org.eclipse.search.ui.text.AbstractTextSearchViewPage$5.open(AbstractTextSearchViewPage.java:702)
at org.eclipse.ui.OpenAndLinkWithEditorHelper$InternalListener.open(OpenAndLinkWithEditorHelper.java:48)
at org.eclipse.jface.viewers.StructuredViewer$2.run(StructuredViewer.java:842)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.runtime.Platform.run(Platform.java:888)
at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:48)
at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
at org.eclipse.jface.viewers.StructuredViewer.fireOpen(StructuredViewer.java:840)
at org.eclipse.jface.viewers.StructuredViewer.handleOpen(StructuredViewer.java:1101)
at org.eclipse.jface.viewers.StructuredViewer$6.handleOpen(StructuredViewer.java:1205)
at org.eclipse.jface.util.OpenStrategy.fireOpenEvent(OpenStrategy.java:264)
at org.eclipse.jface.util.OpenStrategy.access$2(OpenStrategy.java:258)
at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:298)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1003)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3910)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3503)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2405)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2369)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2221)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:500)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:493)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:113)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:194)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:368)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:559)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:514)
at org.eclipse.equinox.launcher.Main.run(Main.java:1311)
at org.eclipse.equinox.launcher.Main.main(Main.java:1287)

Using:

Scala IDE for Eclipse 2.8.0.trunk-t20100705030618-gd7e8fe3a18aec16eb1cffea23b3378ed793cfe69 ch.epfl.lamp.sdt.feature.group

Eclipse SDK

Version: 3.5.2
Build id: M20100211-1343