Building Apache Ant project against the latest EA version of JDK 20, results in the following stacktrace:

 java.lang.UnsupportedOperationException: Not yet implemented
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.taglets.SeeTaglet.inherit(SeeTaglet.java:54)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.taglets.InheritDocTaglet.retrieveInheritedDocumentation(InheritDocTaglet.java:106)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.taglets.InheritDocTaglet.getInlineTagOutput(InheritDocTaglet.java:136)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.taglets.TagletWriter.getInlineTagOutput(TagletWriter.java:358)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.getInlineTagOutput(HtmlDocletWriter.java:372)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter$2.visitInheritDoc(HtmlDocletWriter.java:1345)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter$2.visitInheritDoc(HtmlDocletWriter.java:1225)
    at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCInheritDoc.accept(DCTree.java:731)
    at jdk.compiler/com.sun.source.util.SimpleDocTreeVisitor.visit(SimpleDocTreeVisitor.java:79)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.commentTagsToContent(HtmlDocletWriter.java:1454)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.TagletWriterImpl.seeTagOutput(TagletWriterImpl.java:444)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.TagletWriterImpl.seeTagOutput(TagletWriterImpl.java:360)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.taglets.SeeTaglet.getAllBlockTagOutput(SeeTaglet.java:72)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.taglets.TagletWriter.getBlockTagOutput(TagletWriter.java:321)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.getBlockTagOutput(HtmlDocletWriter.java:355)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.getBlockTagOutput(HtmlDocletWriter.java:341)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.addTagsInfo(HtmlDocletWriter.java:327)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.MethodWriterImpl.addTags(MethodWriterImpl.java:164)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.MethodBuilder.buildTagInfo(MethodBuilder.java:185)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.MethodBuilder.buildMethodDoc(MethodBuilder.java:125)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.MethodBuilder.build(MethodBuilder.java:103)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.buildMethodDetails(ClassBuilder.java:370)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.buildMemberDetails(ClassBuilder.java:318)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.buildClassDoc(ClassBuilder.java:122)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.build(ClassBuilder.java:98)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDoclet.generateClassFiles(HtmlDoclet.java:383)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.generateClassFiles(AbstractDoclet.java:281)
    at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDoclet.generateClassFiles(HtmlDoclet.java:199)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.startGeneration(AbstractDoclet.java:207)
    at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.run(AbstractDoclet.java:110)
    at jdk.javadoc/jdk.javadoc.doclet.StandardDoclet.run(StandardDoclet.java:103)
    at jdk.javadoc/jdk.javadoc.internal.tool.Start.parseAndExecute(Start.java:574)
    at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:397)
    at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:346)
    at jdk.javadoc/jdk.javadoc.internal.tool.Main.execute(Main.java:57)
    at jdk.javadoc/jdk.javadoc.internal.tool.Main.main(Main.java:46)

Building the same project against previous versions of Java, including Java 19, works fine.

Steps to reproduce:
- Clone the Ant project from https://github.com/apache/ant/
- Set JAVA_HOME environment variable to the JDK 20 EA:
export JAVA_HOME=/path/to/jdk-20
- Run the following commands from the root of the cloned repo:
./bootstrap.sh
./build.sh clean javadocs

You will notice the exception stacktrace. To try against any other version of Java, just (re)set the JAVA_HOME environment variable and redo the build steps.