java.lang.AssertionError
   at com.sun.tools.javac.util.Assert.error(Assert.java:155)
   at com.sun.tools.javac.util.Assert.check(Assert.java:46)
   at com.sun.tools.javac.api.JavacTrees.getAttrContext(JavacTrees.java:933)
   at com.sun.tools.javac.api.JavacTrees.getScope(JavacTrees.java:794)
   at com.sun.tools.javac.api.JavacTrees.getScope(JavacTrees.java:156)
   at org.netbeans.modules.java.hints.jdk.ConvertToLambdaPreconditionChecker.getScopeFromTree(ConvertToLambdaPreconditionChecker.java:690)
   at org.netbeans.modules.java.hints.jdk.ConvertToLambdaPreconditionChecker.<init>(ConvertToLambdaPreconditionChecker.java:115)
   at org.netbeans.modules.java.hints.jdk.ConvertToLambda.computeAnnonymousToLambda(ConvertToLambda.java:102)
   at sun.reflect.GeneratedMethodAccessor269.invoke(GeneratedMethodAccessor269.java:0)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:498)
   at org.netbeans.modules.java.hints.providers.code.CodeHintProviderImpl$WorkerImpl.createErrors(CodeHintProviderImpl.java:339)
   at org.netbeans.modules.java.hints.spiimpl.hints.HintsInvoker.runHint(HintsInvoker.java:810)
   at org.netbeans.modules.java.hints.spiimpl.hints.HintsInvoker.doComputeHints(HintsInvoker.java:575)
   at org.netbeans.modules.java.hints.spiimpl.hints.HintsInvoker.computeHintsInSpan(HintsInvoker.java:360)
   at org.netbeans.modules.java.hints.spiimpl.hints.HintsInvoker.computeHints(HintsInvoker.java:236)
   at org.netbeans.modules.java.hints.spiimpl.hints.HintsInvoker.computeHints(HintsInvoker.java:210)
   at org.netbeans.modules.java.hints.spiimpl.hints.HintsInvoker.computeHints(HintsInvoker.java:183)
   at org.netbeans.modules.java.hints.spiimpl.hints.HintsInvoker.computeHints(HintsInvoker.java:150)
   at org.netbeans.modules.java.hints.spiimpl.hints.HintsTask$HintPositionRefresherHelper.getErrorDescriptionsAt(HintsTask.java:228)
   at org.netbeans.modules.java.hints.spiimpl.JavaHintsPositionRefresher$RefreshTask.run(JavaHintsPositionRefresher.java:151)
   at org.netbeans.modules.java.hints.spiimpl.JavaHintsPositionRefresher$RefreshTask.run(JavaHintsPositionRefresher.java:121)
   at org.netbeans.api.java.source.JavaSource$MultiTask.run(JavaSource.java:486)
   at org.netbeans.modules.parsing.impl.TaskProcessor.callUserTask(TaskProcessor.java:609)
   at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:153)
   at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:137)
   at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:204)
   at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:201)
   at org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager.priorityIO(FileChangedManager.java:176)
   at org.netbeans.modules.masterfs.providers.ProvidedExtensions.priorityIO(ProvidedExtensions.java:360)
   at org.netbeans.modules.parsing.nb.DataObjectEnvFactory.runPriorityIO(DataObjectEnvFactory.java:141)
   at org.netbeans.modules.parsing.impl.Utilities.runPriorityIO(Utilities.java:88)
   at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:201)
   at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:104)
   at org.netbeans.api.java.source.JavaSource.runUserActionTaskImpl(JavaSource.java:436)
   at org.netbeans.api.java.source.JavaSource.runUserActionTask(JavaSource.java:407)
   at org.netbeans.modules.java.hints.spiimpl.JavaHintsPositionRefresher$1.run(JavaHintsPositionRefresher.java:108)
   at org.netbeans.modules.progress.ui.RunOffEDTImpl$1.run(RunOffEDTImpl.java:169)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1443)
   at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:68)
   at org.openide.util.lookup.Lookups.executeWith(Lookups.java:303)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2058)