We get a java.util.NoSuchElementException when trying to build the javadoc target for Nashorn using Apache Ant:

  [javadoc] javadoc: error - An exception occurred while building a component: PackagesSummary
  [javadoc] 1 error
  [javadoc] (java.util.NoSuchElementException)
  [javadoc] 3 warnings
  [javadoc] Please file a bug against the javadoc tool via the Java bug reporting page
  [javadoc] (http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com)
  [javadoc] for duplicates. Include error messages and the following diagnostic in your report. Thank you.
  [javadoc] java.util.NoSuchElementException
  [javadoc] at java.base/java.util.RegularEnumSet$EnumSetIterator.next(RegularEnumSet.java:102)
  [javadoc] at java.base/java.util.RegularEnumSet$EnumSetIterator.next(RegularEnumSet.java:78)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.ModuleWriterImpl.addPackageSummary(ModuleWriterImpl.java:585)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.ModuleWriterImpl.addPackagesSummary(ModuleWriterImpl.java:539)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ModuleSummaryBuilder.buildPackagesSummary(ModuleSummaryBuilder.java:187)
  [javadoc] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  [javadoc] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  [javadoc] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  [javadoc] at java.base/java.lang.reflect.Method.invoke(Method.java:538)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.AbstractBuilder.build(AbstractBuilder.java:156)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.AbstractBuilder.buildChildren(AbstractBuilder.java:197)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ModuleSummaryBuilder.buildSummary(ModuleSummaryBuilder.java:165)
  [javadoc] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  [javadoc] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  [javadoc] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  [javadoc] at java.base/java.lang.reflect.Method.invoke(Method.java:538)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.AbstractBuilder.build(AbstractBuilder.java:156)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.AbstractBuilder.buildChildren(AbstractBuilder.java:197)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ModuleSummaryBuilder.buildContent(ModuleSummaryBuilder.java:151)
  [javadoc] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  [javadoc] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  [javadoc] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  [javadoc] at java.base/java.lang.reflect.Method.invoke(Method.java:538)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.AbstractBuilder.build(AbstractBuilder.java:156)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.AbstractBuilder.buildChildren(AbstractBuilder.java:197)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ModuleSummaryBuilder.buildModuleDoc(ModuleSummaryBuilder.java:135)
  [javadoc] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  [javadoc] at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  [javadoc] at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  [javadoc] at java.base/java.lang.reflect.Method.invoke(Method.java:538)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.AbstractBuilder.build(AbstractBuilder.java:156)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ModuleSummaryBuilder.build(ModuleSummaryBuilder.java:115)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDoclet.generateModuleFiles(HtmlDoclet.java:289)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.startGeneration(AbstractDoclet.java:206)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.run(AbstractDoclet.java:115)
  [javadoc] at jdk.javadoc/jdk.javadoc.doclets.StandardDoclet.run(StandardDoclet.java:71)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.tool.Start.parseAndExecute(Start.java:604)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:424)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:341)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.tool.Main.execute(Main.java:63)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.tool.Main.main(Main.java:52)

Looking at the source code, it seems like modulePackageTypes is expected to be empty if showTabs() returns false.

To reproduce, cd into nashorn/make in a jdk9-dev tree and run "ant javadoc".