java.lang.AssertionError
   at com.sun.tools.javac.util.Assert.error(Assert.java:155)
   at com.sun.tools.javac.util.Assert.checkNonNull(Assert.java:62)
   at com.sun.tools.javac.util.ListBuffer.append(ListBuffer.java:127)
   at com.sun.tools.javac.tree.TreeInfo.types(TreeInfo.java:747)
   at com.sun.tools.javac.comp.Attr.visitLambda(Attr.java:2514)
   at com.sun.tools.javac.tree.JCTree$JCLambda.accept(JCTree.java:1777)
   at com.sun.tools.javac.comp.Attr$ResultInfo.attr(Attr.java:496)
   at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:637)
   at com.sun.tools.javac.comp.Attr.attribExpr(Attr.java:683)
   at com.sun.tools.javac.comp.Attr.attribExprToTree(Attr.java:393)
   at com.sun.tools.javac.api.JavacTrees.attribExprToTree(JavacTrees.java:1000)
   at com.sun.tools.javac.api.JavacTrees.getAttrContext(JavacTrees.java:963)
   at com.sun.tools.javac.api.JavacTrees.getScope(JavacTrees.java:797)
   at com.sun.tools.javac.api.JavacTrees.getScope(JavacTrees.java:157)
   at org.netbeans.modules.java.editor.imports.ComputeImports$TreeVisitorImpl.visitIdentifier(ComputeImports.java:572)
   at org.netbeans.modules.java.editor.imports.ComputeImports$TreeVisitorImpl.visitIdentifier(ComputeImports.java:440)
   at com.sun.tools.javac.tree.JCTree$JCIdent.accept(JCTree.java:2202)
   at com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:72)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:94)
   at com.sun.source.util.TreeScanner.scan(TreeScanner.java:106)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:103)
   at org.netbeans.modules.java.editor.imports.ComputeImports$TreeVisitorImpl.visitMethodInvocation(ComputeImports.java:643)
   at org.netbeans.modules.java.editor.imports.ComputeImports$TreeVisitorImpl.visitMethodInvocation(ComputeImports.java:440)
   at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1620)
   at com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:72)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:94)
   at com.sun.source.util.TreeScanner.visitExpressionStatement(TreeScanner.java:434)
   at com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1430)
   at com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:72)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:94)
   at com.sun.source.util.TreeScanner.scan(TreeScanner.java:106)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:103)
   at com.sun.source.util.TreeScanner.visitBlock(TreeScanner.java:249)
   at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1002)
   at com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:72)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:94)
   at com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:91)
   at com.sun.source.util.TreeScanner.visitLambdaExpression(TreeScanner.java:560)
   at com.sun.tools.javac.tree.JCTree$JCLambda.accept(JCTree.java:1781)
   at com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:72)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:94)
   at org.netbeans.modules.java.editor.imports.ComputeImports$TreeVisitorImpl.visitVariable(ComputeImports.java:514)
   at org.netbeans.modules.java.editor.imports.ComputeImports$TreeVisitorImpl.visitVariable(ComputeImports.java:440)
   at com.sun.tools.javac.tree.JCTree$JCVariableDecl.accept(JCTree.java:944)
   at com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:72)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:94)
   at com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:91)
   at com.sun.source.util.TreeScanner.scan(TreeScanner.java:106)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:103)
   at com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:114)
   at com.sun.source.util.TreeScanner.visitClass(TreeScanner.java:188)
   at org.netbeans.modules.java.editor.imports.ComputeImports$TreeVisitorImpl.visitClass(ComputeImports.java:670)
   at org.netbeans.modules.java.editor.imports.ComputeImports$TreeVisitorImpl.visitClass(ComputeImports.java:440)
   at com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:782)
   at com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:72)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:94)
   at com.sun.source.util.TreeScanner.scan(TreeScanner.java:106)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:103)
   at com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:114)
   at com.sun.source.util.TreeScanner.visitCompilationUnit(TreeScanner.java:145)
   at com.sun.tools.javac.tree.JCTree$JCCompilationUnit.accept(JCTree.java:563)
   at com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:72)
   at org.netbeans.api.java.source.support.CancellableTreePathScanner.scan(CancellableTreePathScanner.java:94)
   at org.netbeans.modules.java.editor.imports.ComputeImports.computeCandidates(ComputeImports.java:208)
   at org.netbeans.modules.java.editor.imports.ComputeImports.computeCandidatesEx(ComputeImports.java:184)
   at org.netbeans.modules.java.hints.errors.ImportClass.getCandidateFQNs(ImportClass.java:357)
   at org.netbeans.modules.java.hints.errors.ImportClass.run(ImportClass.java:194)
   at org.netbeans.modules.java.hints.infrastructure.CreatorBasedLazyFixList.compute(CreatorBasedLazyFixList.java:148)
   at org.netbeans.modules.java.hints.infrastructure.LazyHintComputation.run(LazyHintComputation.java:112)
   at org.netbeans.modules.java.hints.infrastructure.LazyHintComputation.run(LazyHintComputation.java:58)
   at org.netbeans.modules.java.source.JavaSourceAccessor$CancelableTaskWrapper.run(JavaSourceAccessor.java:298)
   at org.netbeans.modules.parsing.impl.TaskProcessor.callParserResultTask(TaskProcessor.java:584)
   at org.netbeans.modules.parsing.impl.TaskProcessor$RequestPerformer.run(TaskProcessor.java:809)
   at org.openide.util.lookup.Lookups.executeWith(Lookups.java:304)
   at org.netbeans.modules.parsing.impl.TaskProcessor$RequestPerformer.execute(TaskProcessor.java:725)
   at org.netbeans.modules.parsing.impl.TaskProcessor$CompilationJob.run(TaskProcessor.java:686)
   at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
   at java.util.concurrent.FutureTask.run(FutureTask.java:266)
   at org.openide.util.RequestProcessor$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)