I'm hitting a situation that consistently causes the error below. I'm using groovy compiler 2.4.11. The situation that causes this to happen is a library that I'm using that has the following pattern.

UtilitiesFacade.ioUtils.

Where UtilitiesFacade is a class that has static instances of other classes such as "ioUtils". The error happens when attempting to do code completion after the ioUtils piece. The error happens to other sibling fields also such as "UtilitiesFacade.xUtils."

Eclipse version: Neon
Groovy Eclipse - 2.9.2.xx-201706120159-e46

eclipse.buildId=3.8.4.201703310825-RELEASE-e46
java.version=1.8.0_131
java.vendor=Oracle Corporation
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=en_US
Framework arguments: -product org.springsource.sts.ide
Command-line arguments: -os win32 -ws win32 -arch x86_64 -product org.springsource.sts.ide

org.eclipse.jdt.ui
Warning
Mon Jun 26 09:33:00 PDT 2017
The 'Groovy Code Completions' proposal computer from the 'org.codehaus.groovy.eclipse.codeassist.completion' plug-in did not complete normally. The extension has thrown a runtime exception.

java.lang.IllegalStateException
at org.eclipse.jdt.internal.compiler.lookup.SourceTypeBinding.syntheticMethods(SourceTypeBinding.java:2468)
at org.codehaus.jdt.groovy.internal.compiler.ast.JDTClassNode.initializeMembers(JDTClassNode.java:301)
at org.codehaus.jdt.groovy.internal.compiler.ast.JDTClassNode.initialize(JDTClassNode.java:228)
at org.codehaus.jdt.groovy.internal.compiler.ast.JDTClassNode.lazyClassInit(JDTClassNode.java:159)
at org.codehaus.groovy.ast.ClassNode.getUnresolvedSuperClass(ClassNode.java:1124)
at org.codehaus.groovy.ast.ClassNode.getUnresolvedSuperClass(ClassNode.java:1114)
at org.codehaus.groovy.ast.ClassNode.getSuperClass(ClassNode.java:1108)
at org.codehaus.groovy.ast.ClassNode.getDeclaredMethodsMap(ClassNode.java:528)
at org.codehaus.groovy.ast.ClassNode.getAllDeclaredMethods(ClassNode.java:507)
at org.codehaus.groovy.eclipse.codeassist.creators.AbstractProposalCreator.getAllMethods(AbstractProposalCreator.java:94)
at org.codehaus.groovy.eclipse.codeassist.creators.MethodProposalCreator.findAllProposals(MethodProposalCreator.java:49)
at org.codehaus.groovy.eclipse.codeassist.processors.StatementAndExpressionCompletionProcessor.proposalCreatorLoop(StatementAndExpressionCompletionProcessor.java:456)
at org.codehaus.groovy.eclipse.codeassist.processors.StatementAndExpressionCompletionProcessor.generateProposals(StatementAndExpressionCompletionProcessor.java:350)
at org.codehaus.groovy.eclipse.codeassist.requestor.GroovyCompletionProposalComputer.computeCompletionProposals(GroovyCompletionProposalComputer.java:210)
at org.eclipse.jdt.internal.ui.text.java.CompletionProposalComputerDescriptor.computeCompletionProposals(CompletionProposalComputerDescriptor.java:333)
at org.eclipse.jdt.internal.ui.text.java.CompletionProposalCategory.computeCompletionProposals(CompletionProposalCategory.java:337)
at org.eclipse.jdt.internal.ui.text.java.ContentAssistProcessor.collectProposals(ContentAssistProcessor.java:331)
at org.eclipse.jdt.internal.ui.text.java.ContentAssistProcessor.computeCompletionProposals(ContentAssistProcessor.java:288)
at org.eclipse.jface.text.contentassist.ContentAssistant$3.run(ContentAssistant.java:1931)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.jface.text.contentassist.ContentAssistant.computeCompletionProposals(ContentAssistant.java:1928)
at org.eclipse.jface.text.contentassist.CompletionProposalPopup.computeProposals(CompletionProposalPopup.java:565)
at org.eclipse.jface.text.contentassist.CompletionProposalPopup.access$16(CompletionProposalPopup.java:560)
at org.eclipse.jface.text.contentassist.CompletionProposalPopup$2.run(CompletionProposalPopup.java:494)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.jface.text.contentassist.CompletionProposalPopup.showProposals(CompletionProposalPopup.java:487)
at org.eclipse.jface.text.contentassist.ContentAssistant.showPossibleCompletions(ContentAssistant.java:1747)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitEditor$AdaptedSourceViewer.doOperation(CompilationUnitEditor.java:184)
at org.eclipse.ui.texteditor.ContentAssistAction$1.run(ContentAssistAction.java:84)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.ui.texteditor.ContentAssistAction.run(ContentAssistAction.java:81)
at org.eclipse.jface.action.Action.runWithEvent(Action.java:473)
at org.eclipse.jface.commands.ActionHandler.execute(ActionHandler.java:118)
at org.eclipse.ui.internal.handlers.E4HandlerProxy.execute(E4HandlerProxy.java:90)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:55)
at org.eclipse.e4.core.internal.di.InjectorImpl.invokeUsingClass(InjectorImpl.java:282)
at org.eclipse.e4.core.internal.di.InjectorImpl.invoke(InjectorImpl.java:264)
at org.eclipse.e4.core.contexts.ContextInjectionFactory.invoke(ContextInjectionFactory.java:132)
at org.eclipse.e4.core.commands.internal.HandlerServiceHandler.execute(HandlerServiceHandler.java:152)
at org.eclipse.core.commands.Command.executeWithChecks(Command.java:494)
at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:488)
at org.eclipse.e4.core.commands.internal.HandlerServiceImpl.executeHandler(HandlerServiceImpl.java:210)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.executeCommand(KeyBindingDispatcher.java:286)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.press(KeyBindingDispatcher.java:507)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.processKeyEvent(KeyBindingDispatcher.java:558)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.filterKeySequenceBindings(KeyBindingDispatcher.java:378)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.access$0(KeyBindingDispatcher.java:324)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher$KeyDownFilter.handleEvent(KeyBindingDispatcher.java:86)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Display.filterEvent(Display.java:1270)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1078)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1103)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1088)
at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1130)
at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1126)
at org.eclipse.swt.widgets.Widget.wmChar(Widget.java:1547)
at org.eclipse.swt.widgets.Control.WM_CHAR(Control.java:4918)
at org.eclipse.swt.widgets.Canvas.WM_CHAR(Canvas.java:364)
at org.eclipse.swt.widgets.Control.windowProc(Control.java:4799)
at org.eclipse.swt.widgets.Canvas.windowProc(Canvas.java:359)
at org.eclipse.swt.widgets.Display.windowProc(Display.java:5110)
at org.eclipse.swt.internal.win32.OS.DispatchMessageW(Native Method)
at org.eclipse.swt.internal.win32.OS.DispatchMessage(OS.java:2552)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3822)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1121)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1022)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:150)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:693)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:610)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:148)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:138)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:388)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:243)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:673)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:610)
at org.eclipse.equinox.launcher.Main.run(Main.java:1519)