Can't start Less editor

[machineghost]

I got an error a few minutes ago and now I can't even start the Less editor. I've tried closing Eclipse, deleting my dropins file, restarting Eclipse, closing Eclipse, restoring the dropins folder, and restarting Eclipse yet again ... and it still doesn't work.

The Eclipse message (when I try to open a file in the Less editor) is "Could not open the editor: Editor could not be initialized.", and the stack trace is as follows. Any help would be appreciated.

org.eclipse.xtext.parser.ParseException: org.eclipse.xtext.conversion.ValueConverterException: nl.dslmeinte.xtext.css.css.impl.DescendantCombinatorImpl cannot be cast to nl.dslmeinte.xtext.css.css.SimpleSelectorSequence
at org.eclipse.xtext.parser.antlr.AbstractAntlrParser.doParse(AbstractAntlrParser.java:105)
at org.eclipse.xtext.parser.antlr.AbstractAntlrParser.parse(AbstractAntlrParser.java:84)
at org.eclipse.xtext.parser.antlr.AbstractAntlrParser.doParse(AbstractAntlrParser.java:62)
at org.eclipse.xtext.parser.AbstractParser.parse(AbstractParser.java:27)
at org.eclipse.xtext.resource.XtextResource.doLoad(XtextResource.java:156)
at org.eclipse.xtext.linking.lazy.LazyLinkingResource.doLoad(LazyLinkingResource.java:70)
at org.eclipse.emf.ecore.resource.impl.ResourceImpl.load(ResourceImpl.java:1511)
at org.eclipse.xtext.ui.editor.model.XtextDocumentProvider.loadResource(XtextDocumentProvider.java:142)
at org.eclipse.xtext.ui.editor.model.XtextDocumentProvider.setDocumentContent(XtextDocumentProvider.java:119)
at org.eclipse.ui.editors.text.StorageDocumentProvider.createDocument(StorageDocumentProvider.java:229)
at org.eclipse.xtext.ui.editor.model.XtextDocumentProvider.createDocument(XtextDocumentProvider.java:88)
at org.eclipse.ui.editors.text.FileDocumentProvider.createElementInfo(FileDocumentProvider.java:735)
at org.eclipse.xtext.ui.editor.model.XtextDocumentProvider.createElementInfo(XtextDocumentProvider.java:153)
at org.eclipse.ui.texteditor.AbstractDocumentProvider.connect(AbstractDocumentProvider.java:400)
at org.eclipse.ui.texteditor.AbstractTextEditor.doSetInput(AbstractTextEditor.java:4213)
at org.eclipse.ui.texteditor.StatusTextEditor.doSetInput(StatusTextEditor.java:237)
at org.eclipse.ui.texteditor.AbstractDecoratedTextEditor.doSetInput(AbstractDecoratedTextEditor.java:1451)
at org.eclipse.ui.editors.text.TextEditor.doSetInput(TextEditor.java:169)
at org.eclipse.xtext.ui.editor.XtextEditor.doSetInput(XtextEditor.java:190)
at org.eclipse.ui.texteditor.AbstractTextEditor$19.run(AbstractTextEditor.java:3200)
at org.eclipse.jface.operation.ModalContext.runInCurrentThread(ModalContext.java:464)
at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:372)
at org.eclipse.jface.window.ApplicationWindow$1.run(ApplicationWindow.java:759)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.jface.window.ApplicationWindow.run(ApplicationWindow.java:756)
at org.eclipse.ui.internal.WorkbenchWindow.run(WorkbenchWindow.java:2642)
at org.eclipse.ui.texteditor.AbstractTextEditor.internalInit(AbstractTextEditor.java:3218)
at org.eclipse.ui.texteditor.AbstractTextEditor.init(AbstractTextEditor.java:3245)
at org.eclipse.xtext.ui.editor.XtextEditor.init(XtextEditor.java:211)
at org.eclipse.ui.internal.EditorManager.createSite(EditorManager.java:828)
at org.eclipse.ui.internal.EditorReference.createPartHelper(EditorReference.java:647)
at org.eclipse.ui.internal.EditorReference.createPart(EditorReference.java:465)
at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:595)
at org.eclipse.ui.internal.EditorReference.getEditor(EditorReference.java:289)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditorBatched(WorkbenchPage.java:2945)
at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditor(WorkbenchPage.java:2850)
at org.eclipse.ui.internal.WorkbenchPage.access$11(WorkbenchPage.java:2842)
at org.eclipse.ui.internal.WorkbenchPage$10.run(WorkbenchPage.java:2793)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2789)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2773)
at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2764)
at org.eclipse.ui.ide.IDE.openEditor(IDE.java:651)
at org.eclipse.ui.ide.IDE.openEditor(IDE.java:610)
at org.eclipse.ui.internal.ide.handlers.OpenResourceHandler.execute(OpenResourceHandler.java:129)
at org.eclipse.ui.internal.ide.handlers.OpenResourceHandler.run(OpenResourceHandler.java:181)
at org.eclipse.ui.internal.handlers.ActionDelegateHandlerProxy.execute(ActionDelegateHandlerProxy.java:289)
at org.eclipse.core.commands.Command.executeWithChecks(Command.java:476)
at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:508)
at org.eclipse.ui.internal.handlers.HandlerService.executeCommand(HandlerService.java:169)
at org.eclipse.ui.internal.keys.WorkbenchKeyboard.executeCommand(WorkbenchKeyboard.java:468)
at org.eclipse.ui.internal.keys.WorkbenchKeyboard.press(WorkbenchKeyboard.java:786)
at org.eclipse.ui.internal.keys.WorkbenchKeyboard.processKeyEvent(WorkbenchKeyboard.java:885)
at org.eclipse.ui.internal.keys.WorkbenchKeyboard.filterKeySequenceBindings(WorkbenchKeyboard.java:567)
at org.eclipse.ui.internal.keys.WorkbenchKeyboard.access$3(WorkbenchKeyboard.java:508)
at org.eclipse.ui.internal.keys.WorkbenchKeyboard$KeyDownFilter.handleEvent(WorkbenchKeyboard.java:123)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Display.filterEvent(Display.java:1531)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1257)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1282)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1267)
at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1294)
at org.eclipse.swt.widgets.Widget.gtk_key_press_event(Widget.java:730)
at org.eclipse.swt.widgets.Control.gtk_key_press_event(Control.java:3019)
at org.eclipse.swt.widgets.Composite.gtk_key_press_event(Composite.java:734)
at org.eclipse.swt.widgets.Widget.windowProc(Widget.java:1743)
at org.eclipse.swt.widgets.Control.windowProc(Control.java:5016)
at org.eclipse.swt.widgets.Display.windowProc(Display.java:4408)
at org.eclipse.swt.internal.gtk.OS._gtk_main_do_event(Native Method)
at org.eclipse.swt.internal.gtk.OS.gtk_main_do_event(OS.java:8422)
at org.eclipse.swt.widgets.Display.eventProc(Display.java:1245)
at org.eclipse.swt.internal.gtk.OS._g_main_context_iteration(Native Method)
at org.eclipse.swt.internal.gtk.OS.g_main_context_iteration(OS.java:2276)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3207)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2696)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2660)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2494)
at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:674)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:667)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:123)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
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:344)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:622)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:577)
at org.eclipse.equinox.launcher.Main.run(Main.java:1410)
at org.eclipse.equinox.launcher.Main.main(Main.java:1386)
Caused by: org.eclipse.emf.common.util.WrappedException: org.eclipse.xtext.conversion.ValueConverterException: nl.dslmeinte.xtext.css.css.impl.DescendantCombinatorImpl cannot be cast to nl.dslmeinte.xtext.css.css.SimpleSelectorSequence
at org.eclipse.xtext.parser.antlr.AbstractInternalAntlrParser.parse(AbstractInternalAntlrParser.java:551)
at org.eclipse.xtext.parser.antlr.AbstractAntlrParser.doParse(AbstractAntlrParser.java:102)
... 94 more
Caused by: org.eclipse.xtext.conversion.ValueConverterException: nl.dslmeinte.xtext.css.css.impl.DescendantCombinatorImpl cannot be cast to nl.dslmeinte.xtext.css.css.SimpleSelectorSequence
at org.eclipse.xtext.parser.DefaultEcoreElementFactory.set(DefaultEcoreElementFactory.java:80)
at org.eclipse.xtext.parser.antlr.AbstractInternalAntlrParser.forceCreateModelElementAndSet(AbstractInternalAntlrParser.java:637)
at nl.dslmeinte.xtext.less.parser.antlr.internal.InternalLessParser.ruleCombinatorExpression(InternalLessParser.java:5657)
at nl.dslmeinte.xtext.less.parser.antlr.internal.InternalLessParser.ruleSelector(InternalLessParser.java:5468)
at nl.dslmeinte.xtext.less.parser.antlr.internal.InternalLessParser.ruleExtendedRuleSet(InternalLessParser.java:995)
at nl.dslmeinte.xtext.less.parser.antlr.internal.InternalLessParser.ruleStatement(InternalLessParser.java:422)
at nl.dslmeinte.xtext.less.parser.antlr.internal.InternalLessParser.ruleLessFile(InternalLessParser.java:243)
at nl.dslmeinte.xtext.less.parser.antlr.internal.InternalLessParser.entryRuleLessFile(InternalLessParser.java:185)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.eclipse.xtext.parser.antlr.AbstractInternalAntlrParser.parse(AbstractInternalAntlrParser.java:528)
... 95 more
Caused by: java.lang.ClassCastException: nl.dslmeinte.xtext.css.css.impl.DescendantCombinatorImpl cannot be cast to nl.dslmeinte.xtext.css.css.SimpleSelectorSequence
at nl.dslmeinte.xtext.css.css.impl.DescendantCombinatorImpl.eSet(DescendantCombinatorImpl.java:266)
at org.eclipse.emf.ecore.impl.BasicEObjectImpl.eSet(BasicEObjectImpl.java:1081)
at org.eclipse.xtext.parser.DefaultEcoreElementFactory.set(DefaultEcoreElementFactory.java:69)
... 107 more

[dslmeinte]

This is a problem in the grammar and more specifically a problem with the interaction between the parser generated by ANTLR and the Xtext parsing runtime (and the way the Xtext generator generates the ANTLR grammar). It's a part of the grammar which probably needs to be re-written anyhow. Unfortunately, I've got no time at all to look into it.

You should be able to partly "fix" your Eclipse by opening the file in another editor. Manipulating the dropins folder (other than installing the fixed version of the plug-ins once they exist) is useless.

[machineghost]

Thanks for the response