java.lang.ClassCastException: com.sun.tools.javac.code.Type$ForAll cannot be cast to com.sun.tools.javac.code.Type$MethodType
   at org.netbeans.api.java.source.ElementUtilities.findUnimplementedMethods(ElementUtilities.java:812)
   at org.netbeans.api.java.source.ElementUtilities.findUnimplementedMethods(ElementUtilities.java:792)
   at org.netbeans.api.java.source.ElementUtilities.findUnimplementedMethods(ElementUtilities.java:574)
   at org.netbeans.modules.java.completion.JavaCompletionTask.addElementCreators(JavaCompletionTask.java:4206)
   at org.netbeans.modules.java.completion.JavaCompletionTask.insideClass(JavaCompletionTask.java:503)
   at org.netbeans.modules.java.completion.JavaCompletionTask.resolve(JavaCompletionTask.java:286)
   at org.netbeans.modules.java.completion.BaseTask.run(BaseTask.java:92)
   at org.netbeans.modules.java.completion.JavaCompletionTask.run(JavaCompletionTask.java:80)
   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$2.call(TaskProcessor.java:201)
   at org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager.priorityIO(FileChangedManager.java:176)
   at org.netbeans.modules.masterfs.providers.ProvidedExtensions.priorityIO(ProvidedExtensions.java:360)
   at org.netbeans.modules.parsing.nb.DataObjectEnvFactory.runPriorityIO(DataObjectEnvFactory.java:141)
   at org.netbeans.modules.parsing.impl.Utilities.runPriorityIO(Utilities.java:88)
Caused: org.netbeans.modules.parsing.spi.ParseException
   at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:209)
   at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:104)
   at org.netbeans.modules.editor.java.JavaCompletionProvider$JavaCompletionQuery.query(JavaCompletionProvider.java:234)
   at org.netbeans.spi.editor.completion.support.AsyncCompletionTask.run(AsyncCompletionTask.java:223)
   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)