diff -r 4ebc2e2fb97c -r 71c04702a3d5 test/langtools/tools/javac/tree/TreePosTest.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/langtools/tools/javac/tree/TreePosTest.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,777 @@
+/*
+ * Copyright (c) 2010, 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.awt.BorderLayout;
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.EventQueue;
+import java.awt.Font;
+import java.awt.GridBagConstraints;
+import java.awt.GridBagLayout;
+import java.awt.Rectangle;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.event.MouseAdapter;
+import java.awt.event.MouseEvent;
+import java.io.File;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.nio.charset.Charset;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import javax.swing.DefaultComboBoxModel;
+import javax.swing.JComboBox;
+import javax.swing.JComponent;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+import javax.swing.JScrollPane;
+import javax.swing.JTextArea;
+import javax.swing.JTextField;
+import javax.swing.SwingUtilities;
+import javax.swing.event.CaretEvent;
+import javax.swing.event.CaretListener;
+import javax.swing.text.BadLocationException;
+import javax.swing.text.DefaultHighlighter;
+import javax.swing.text.Highlighter;
+import javax.tools.Diagnostic;
+import javax.tools.DiagnosticListener;
+import javax.tools.JavaFileObject;
+import javax.tools.StandardJavaFileManager;
+
+import com.sun.source.tree.CompilationUnitTree;
+import com.sun.source.util.JavacTask;
+import com.sun.tools.javac.api.JavacTool;
+import com.sun.tools.javac.code.Flags;
+import com.sun.tools.javac.tree.EndPosTable;
+import com.sun.tools.javac.tree.JCTree;
+import com.sun.tools.javac.tree.JCTree.JCAnnotatedType;
+import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
+import com.sun.tools.javac.tree.JCTree.JCNewClass;
+import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
+import com.sun.tools.javac.tree.TreeInfo;
+import com.sun.tools.javac.tree.TreeScanner;
+
+import static com.sun.tools.javac.tree.JCTree.Tag.*;
+import static com.sun.tools.javac.util.Position.NOPOS;
+
+/**
+ * Utility and test program to check validity of tree positions for tree nodes.
+ * The program can be run standalone, or as a jtreg test.  In standalone mode,
+ * errors can be displayed in a gui viewer. For info on command line args,
+ * run program with no args.
+ *
+ * <p>
+ * jtreg: Note that by using the -r switch in the test description below, this test
+ * will process all java files in the langtools/test directory, thus implicitly
+ * covering any new language features that may be tested in this test suite.
+ */
+
+/*
+ * @test
+ * @bug 6919889
+ * @summary assorted position errors in compiler syntax trees
+ * OLD: -q -r -ef ./tools/javac/typeAnnotations -ef ./tools/javap/typeAnnotations -et ANNOTATED_TYPE .
+ * @modules java.desktop
+ *          jdk.compiler/com.sun.tools.javac.api
+ *          jdk.compiler/com.sun.tools.javac.code
+ *          jdk.compiler/com.sun.tools.javac.file
+ *          jdk.compiler/com.sun.tools.javac.tree
+ *          jdk.compiler/com.sun.tools.javac.util
+ * @run main TreePosTest -q -r .
+ */
+public class TreePosTest {
+    /**
+     * Main entry point.
+     * If test.src is set, program runs in jtreg mode, and will throw an Error
+     * if any errors arise, otherwise System.exit will be used, unless the gui
+     * viewer is being used. In jtreg mode, the default base directory for file
+     * args is the value of ${test.src}. In jtreg mode, the -r option can be
+     * given to change the default base directory to the root test directory.
+     */
+    public static void main(String... args) throws IOException {
+        String testSrc = System.getProperty("test.src");
+        File baseDir = (testSrc == null) ? null : new File(testSrc);
+        boolean ok = new TreePosTest().run(baseDir, args);
+        if (!ok) {
+            if (testSrc != null)  // jtreg mode
+                throw new Error("failed");
+            else
+                System.exit(1);
+        }
+    }
+
+    /**
+     * Run the program. A base directory can be provided for file arguments.
+     * In jtreg mode, the -r option can be given to change the default base
+     * directory to the test root directory. For other options, see usage().
+     * @param baseDir base directory for any file arguments.
+     * @param args command line args
+     * @return true if successful or in gui mode
+     */
+    boolean run(File baseDir, String... args) throws IOException {
+        try {
+            if (args.length == 0) {
+                usage(System.out);
+                return true;
+            }
+
+            List<File> files = new ArrayList<File>();
+            for (int i = 0; i < args.length; i++) {
+                String arg = args[i];
+                if (arg.equals("-encoding") && i + 1 < args.length)
+                    encoding = args[++i];
+                else if (arg.equals("-gui"))
+                    gui = true;
+                else if (arg.equals("-q"))
+                    quiet = true;
+                else if (arg.equals("-v"))
+                    verbose = true;
+                else if (arg.equals("-t") && i + 1 < args.length)
+                    tags.add(args[++i]);
+                else if (arg.equals("-ef") && i + 1 < args.length)
+                    excludeFiles.add(new File(baseDir, args[++i]));
+                else if (arg.equals("-et") && i + 1 < args.length)
+                    excludeTags.add(args[++i]);
+                else if (arg.equals("-r")) {
+                    if (excludeFiles.size() > 0)
+                        throw new Error("-r must be used before -ef");
+                    File d = baseDir;
+                    while (!new File(d, "TEST.ROOT").exists()) {
+                        d = d.getParentFile();
+                        if (d == null)
+                            throw new Error("cannot find TEST.ROOT");
+                    }
+                    baseDir = d;
+                }
+                else if (arg.startsWith("-"))
+                    throw new Error("unknown option: " + arg);
+                else {
+                    while (i < args.length)
+                        files.add(new File(baseDir, args[i++]));
+                }
+            }
+
+            for (File file: files) {
+                if (file.exists())
+                    test(file);
+                else
+                    error("File not found: " + file);
+            }
+
+            if (fileCount != 1)
+                System.err.println(fileCount + " files read");
+            if (errors > 0)
+                System.err.println(errors + " errors");
+
+            return (gui || errors == 0);
+        } finally {
+            fm.close();
+        }
+    }
+
+    /**
+     * Print command line help.
+     * @param out output stream
+     */
+    void usage(PrintStream out) {
+        out.println("Usage:");
+        out.println("  java TreePosTest options... files...");
+        out.println("");
+        out.println("where options include:");
+        out.println("-gui      Display returns in a GUI viewer");
+        out.println("-q        Quiet: don't report on inapplicable files");
+        out.println("-v        Verbose: report on files as they are being read");
+        out.println("-t tag    Limit checks to tree nodes with this tag");
+        out.println("          Can be repeated if desired");
+        out.println("-ef file  Exclude file or directory");
+        out.println("-et tag   Exclude tree nodes with given tag name");
+        out.println("");
+        out.println("files may be directories or files");
+        out.println("directories will be scanned recursively");
+        out.println("non java files, or java files which cannot be parsed, will be ignored");
+        out.println("");
+    }
+
+    /**
+     * Test a file. If the file is a directory, it will be recursively scanned
+     * for java files.
+     * @param file the file or directory to test
+     */
+    void test(File file) {
+        if (excludeFiles.contains(file)) {
+            if (!quiet)
+                error("File " + file + " excluded");
+            return;
+        }
+
+        if (file.isDirectory()) {
+            for (File f: file.listFiles()) {
+                test(f);
+            }
+            return;
+        }
+
+        if (file.isFile() && file.getName().endsWith(".java")) {
+            try {
+                if (verbose)
+                    System.err.println(file);
+                fileCount++;
+                PosTester p = new PosTester();
+                p.test(read(file));
+            } catch (ParseException e) {
+                if (!quiet) {
+                    error("Error parsing " + file + "\n" + e.getMessage());
+                }
+            } catch (IOException e) {
+                error("Error reading " + file + ": " + e);
+            }
+            return;
+        }
+
+        if (!quiet)
+            error("File " + file + " ignored");
+    }
+
+    // See CR:  6982992 Tests CheckAttributedTree.java, JavacTreeScannerTest.java, and SourceTreeeScannerTest.java timeout
+    StringWriter sw = new StringWriter();
+    PrintWriter pw = new PrintWriter(sw);
+    Reporter r = new Reporter(pw);
+    JavacTool tool = JavacTool.create();
+    StandardJavaFileManager fm = tool.getStandardFileManager(r, null, null);
+
+    /**
+     * Read a file.
+     * @param file the file to be read
+     * @return the tree for the content of the file
+     * @throws IOException if any IO errors occur
+     * @throws TreePosTest.ParseException if any errors occur while parsing the file
+     */
+    JCCompilationUnit read(File file) throws IOException, ParseException {
+        JavacTool tool = JavacTool.create();
+        r.errors = 0;
+        Iterable<? extends JavaFileObject> files = fm.getJavaFileObjects(file);
+        JavacTask task = tool.getTask(pw, fm, r, List.of("-proc:none"), null, files);
+        Iterable<? extends CompilationUnitTree> trees = task.parse();
+        pw.flush();
+        if (r.errors > 0)
+            throw new ParseException(sw.toString());
+        Iterator<? extends CompilationUnitTree> iter = trees.iterator();
+        if (!iter.hasNext())
+            throw new Error("no trees found");
+        JCCompilationUnit t = (JCCompilationUnit) iter.next();
+        if (iter.hasNext())
+            throw new Error("too many trees found");
+        return t;
+    }
+
+    /**
+     * Report an error. When the program is complete, the program will either
+     * exit or throw an Error if any errors have been reported.
+     * @param msg the error message
+     */
+    void error(String msg) {
+        System.err.println(msg);
+        errors++;
+    }
+
+    /**
+     * Names for tree tags.
+     */
+    private static String getTagName(JCTree.Tag tag) {
+        String name = tag.name();
+        return (name == null) ? "??" : name;
+    }
+
+    /** Number of files that have been analyzed. */
+    int fileCount;
+    /** Number of errors reported. */
+    int errors;
+    /** Flag: don't report irrelevant files. */
+    boolean quiet;
+    /** Flag: report files as they are processed. */
+    boolean verbose;
+    /** Flag: show errors in GUI viewer. */
+    boolean gui;
+    /** Option: encoding for test files. */
+    String encoding;
+    /** The GUI viewer for errors. */
+    Viewer viewer;
+    /** The set of tags for tree nodes to be analyzed; if empty, all tree nodes
+     * are analyzed. */
+    Set<String> tags = new HashSet<String>();
+    /** Set of files and directories to be excluded from analysis. */
+    Set<File> excludeFiles = new HashSet<File>();
+    /** Set of tag names to be excluded from analysis. */
+    Set<String> excludeTags = new HashSet<String>();
+
+    /**
+     * Main class for testing assertions concerning tree positions for tree nodes.
+     */
+    private class PosTester extends TreeScanner {
+        void test(JCCompilationUnit tree) {
+            sourcefile = tree.sourcefile;
+            endPosTable = tree.endPositions;
+            encl = new Info();
+            tree.accept(this);
+        }
+
+        @Override
+        public void scan(JCTree tree) {
+            if (tree == null)
+                return;
+
+            Info self = new Info(tree, endPosTable);
+            if (check(encl, self)) {
+                // Modifiers nodes are present throughout the tree even where
+                // there is no corresponding source text.
+                // Redundant semicolons in a class definition can cause empty
+                // initializer blocks with no positions.
+                if ((self.tag == MODIFIERS || self.tag == BLOCK)
+                        && self.pos == NOPOS) {
+                    // If pos is NOPOS, so should be the start and end positions
+                    check("start == NOPOS", encl, self, self.start == NOPOS);
+                    check("end == NOPOS", encl, self, self.end == NOPOS);
+                } else {
+                    // For this node, start , pos, and endpos should be all defined
+                    check("start != NOPOS", encl, self, self.start != NOPOS);
+                    check("pos != NOPOS", encl, self, self.pos != NOPOS);
+                    check("end != NOPOS", encl, self, self.end != NOPOS);
+                    // The following should normally be ordered
+                    // encl.start <= start <= pos <= end <= encl.end
+                    // In addition, the position of the enclosing node should be
+                    // within this node.
+                    // The primary exceptions are for array type nodes, because of the
+                    // need to support legacy syntax:
+                    //    e.g.    int a[];    int[] b[];    int f()[] { return null; }
+                    // and because of inconsistent nesting of left and right of
+                    // array declarations:
+                    //    e.g.    int[][] a = new int[2][];
+                    if (!(encl.tag == REFERENCE && self.tag == ANNOTATED_TYPE)) {
+                    check("encl.start <= start", encl, self, encl.start <= self.start);
+                    }
+                    check("start <= pos", encl, self, self.start <= self.pos);
+                    if (!( (self.tag == TYPEARRAY ||
+                            isAnnotatedArray(self.tree))
+                            && (encl.tag == VARDEF ||
+                                encl.tag == METHODDEF ||
+                                encl.tag == TYPEARRAY ||
+                                isAnnotatedArray(encl.tree))
+                           ||
+                            encl.tag == ANNOTATED_TYPE && self.tag == SELECT
+                           ||
+                            encl.tag == REFERENCE && self.tag == ANNOTATED_TYPE
+                         )) {
+                        check("encl.pos <= start || end <= encl.pos",
+                                encl, self, encl.pos <= self.start || self.end <= encl.pos);
+                    }
+                    check("pos <= end", encl, self, self.pos <= self.end);
+                    if (!( (self.tag == TYPEARRAY || isAnnotatedArray(self.tree)) &&
+                            (encl.tag == TYPEARRAY || isAnnotatedArray(encl.tree))
+                           ||
+                            encl.tag == MODIFIERS && self.tag == ANNOTATION
+                         ) ) {
+                        check("end <= encl.end", encl, self, self.end <= encl.end);
+                    }
+                }
+            }
+
+            Info prevEncl = encl;
+            encl = self;
+            tree.accept(this);
+            encl = prevEncl;
+        }
+
+        private boolean isAnnotatedArray(JCTree tree) {
+            return tree.hasTag(ANNOTATED_TYPE) &&
+                            ((JCAnnotatedType)tree).underlyingType.hasTag(TYPEARRAY);
+        }
+
+        @Override
+        public void visitVarDef(JCVariableDecl tree) {
+            // enum member declarations are desugared in the parser and have
+            // ill-defined semantics for tree positions, so for now, we
+            // skip the synthesized bits and just check parts which came from
+            // the original source text
+            if ((tree.mods.flags & Flags.ENUM) != 0) {
+                scan(tree.mods);
+                if (tree.init != null) {
+                    if (tree.init.hasTag(NEWCLASS)) {
+                        JCNewClass init = (JCNewClass) tree.init;
+                        if (init.args != null && init.args.nonEmpty()) {
+                            scan(init.args);
+                        }
+                        if (init.def != null && init.def.defs != null) {
+                            scan(init.def.defs);
+                        }
+                    }
+                }
+            } else
+                super.visitVarDef(tree);
+        }
+
+        boolean check(Info encl, Info self) {
+            if (excludeTags.size() > 0) {
+                if (encl != null && excludeTags.contains(getTagName(encl.tag))
+                        || excludeTags.contains(getTagName(self.tag)))
+                    return false;
+            }
+            return tags.size() == 0 || tags.contains(getTagName(self.tag));
+        }
+
+        void check(String label, Info encl, Info self, boolean ok) {
+            if (!ok) {
+                if (gui) {
+                    if (viewer == null)
+                        viewer = new Viewer();
+                    viewer.addEntry(sourcefile, label, encl, self);
+                }
+
+                String s = "encl: " + encl.tree.toString() +
+                        "  this: " + self.tree.toString();
+                String msg = sourcefile.getName() + ": " + label + ": " +
+                        "encl:" + encl + " this:" + self + "\n" +
+                        s.substring(0, Math.min(80, s.length())).replaceAll("[\r\n]+", " ");
+                error(msg);
+            }
+        }
+
+        JavaFileObject sourcefile;
+        EndPosTable endPosTable;
+        Info encl;
+
+    }
+
+    /**
+     * Utility class providing easy access to position and other info for a tree node.
+     */
+    private class Info {
+        Info() {
+            tree = null;
+            tag = ERRONEOUS;
+            start = 0;
+            pos = 0;
+            end = Integer.MAX_VALUE;
+        }
+
+        Info(JCTree tree, EndPosTable endPosTable) {
+            this.tree = tree;
+            tag = tree.getTag();
+            start = TreeInfo.getStartPos(tree);
+            pos = tree.pos;
+            end = TreeInfo.getEndPos(tree, endPosTable);
+        }
+
+        @Override
+        public String toString() {
+            return getTagName(tree.getTag()) + "[start:" + start + ",pos:" + pos + ",end:" + end + "]";
+        }
+
+        final JCTree tree;
+        final JCTree.Tag tag;
+        final int start;
+        final int pos;
+        final int end;
+    }
+
+    /**
+     * Thrown when errors are found parsing a java file.
+     */
+    private static class ParseException extends Exception {
+        ParseException(String msg) {
+            super(msg);
+        }
+    }
+
+    /**
+     * DiagnosticListener to report diagnostics and count any errors that occur.
+     */
+    private static class Reporter implements DiagnosticListener<JavaFileObject> {
+        Reporter(PrintWriter out) {
+            this.out = out;
+        }
+
+        public void report(Diagnostic<? extends JavaFileObject> diagnostic) {
+            out.println(diagnostic);
+            switch (diagnostic.getKind()) {
+                case ERROR:
+                    errors++;
+            }
+        }
+        int errors;
+        PrintWriter out;
+    }
+
+    /**
+     * GUI viewer for issues found by TreePosTester. The viewer provides a drop
+     * down list for selecting error conditions, a header area providing details
+     * about an error, and a text area with the ranges of text highlighted as
+     * appropriate.
+     */
+    private class Viewer extends JFrame {
+        /**
+         * Create a viewer.
+         */
+        Viewer() {
+            initGUI();
+        }
+
+        /**
+         * Add another entry to the list of errors.
+         * @param file The file containing the error
+         * @param check The condition that was being tested, and which failed
+         * @param encl the enclosing tree node
+         * @param self the tree node containing the error
+         */
+        void addEntry(JavaFileObject file, String check, Info encl, Info self) {
+            Entry e = new Entry(file, check, encl, self);
+            DefaultComboBoxModel m = (DefaultComboBoxModel) entries.getModel();
+            m.addElement(e);
+            if (m.getSize() == 1)
+                entries.setSelectedItem(e);
+        }
+
+        /**
+         * Initialize the GUI window.
+         */
+        private void initGUI() {
+            JPanel head = new JPanel(new GridBagLayout());
+            GridBagConstraints lc = new GridBagConstraints();
+            GridBagConstraints fc = new GridBagConstraints();
+            fc.anchor = GridBagConstraints.WEST;
+            fc.fill = GridBagConstraints.HORIZONTAL;
+            fc.gridwidth = GridBagConstraints.REMAINDER;
+
+            entries = new JComboBox();
+            entries.addActionListener(new ActionListener() {
+                public void actionPerformed(ActionEvent e) {
+                    showEntry((Entry) entries.getSelectedItem());
+                }
+            });
+            fc.insets.bottom = 10;
+            head.add(entries, fc);
+            fc.insets.bottom = 0;
+            head.add(new JLabel("check:"), lc);
+            head.add(checkField = createTextField(80), fc);
+            fc.fill = GridBagConstraints.NONE;
+            head.add(setBackground(new JLabel("encl:"), enclColor), lc);
+            head.add(enclPanel = new InfoPanel(), fc);
+            head.add(setBackground(new JLabel("self:"), selfColor), lc);
+            head.add(selfPanel = new InfoPanel(), fc);
+            add(head, BorderLayout.NORTH);
+
+            body = new JTextArea();
+            body.setFont(Font.decode(Font.MONOSPACED));
+            body.addCaretListener(new CaretListener() {
+                public void caretUpdate(CaretEvent e) {
+                    int dot = e.getDot();
+                    int mark = e.getMark();
+                    if (dot == mark)
+                        statusText.setText("dot: " + dot);
+                    else
+                        statusText.setText("dot: " + dot + ", mark:" + mark);
+                }
+            });
+            JScrollPane p = new JScrollPane(body,
+                    JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
+                    JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
+            p.setPreferredSize(new Dimension(640, 480));
+            add(p, BorderLayout.CENTER);
+
+            statusText = createTextField(80);
+            add(statusText, BorderLayout.SOUTH);
+
+            pack();
+            setLocationRelativeTo(null); // centered on screen
+            setVisible(true);
+            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        }
+
+        /** Show an entry that has been selected. */
+        private void showEntry(Entry e) {
+            try {
+                // update simple fields
+                setTitle(e.file.getName());
+                checkField.setText(e.check);
+                enclPanel.setInfo(e.encl);
+                selfPanel.setInfo(e.self);
+                // show file text with highlights
+                body.setText(e.file.getCharContent(true).toString());
+                Highlighter highlighter = body.getHighlighter();
+                highlighter.removeAllHighlights();
+                addHighlight(highlighter, e.encl, enclColor);
+                addHighlight(highlighter, e.self, selfColor);
+                scroll(body, getMinPos(enclPanel.info, selfPanel.info));
+            } catch (IOException ex) {
+                body.setText("Cannot read " + e.file.getName() + ": " + e);
+            }
+        }
+
+        /** Create a test field. */
+        private JTextField createTextField(int width) {
+            JTextField f = new JTextField(width);
+            f.setEditable(false);
+            f.setBorder(null);
+            return f;
+        }
+
+        /** Add a highlighted region based on the positions in an Info object. */
+        private void addHighlight(Highlighter h, Info info, Color c) {
+            int start = info.start;
+            int end = info.end;
+            if (start == -1 && end == -1)
+                return;
+            if (start == -1)
+                start = end;
+            if (end == -1)
+                end = start;
+            try {
+                h.addHighlight(info.start, info.end,
+                        new DefaultHighlighter.DefaultHighlightPainter(c));
+                if (info.pos != -1) {
+                    Color c2 = new Color(c.getRed(), c.getGreen(), c.getBlue(), (int)(.4f * 255)); // 40%
+                    h.addHighlight(info.pos, info.pos + 1,
+                        new DefaultHighlighter.DefaultHighlightPainter(c2));
+                }
+            } catch (BadLocationException e) {
+                e.printStackTrace();
+            }
+        }
+
+        /** Get the minimum valid position in a set of info objects. */
+        private int getMinPos(Info... values) {
+            int i = Integer.MAX_VALUE;
+            for (Info info: values) {
+                if (info.start >= 0) i = Math.min(i, info.start);
+                if (info.pos   >= 0) i = Math.min(i, info.pos);
+                if (info.end   >= 0) i = Math.min(i, info.end);
+            }
+            return (i == Integer.MAX_VALUE) ? 0 : i;
+        }
+
+        /** Set the background on a component. */
+        private JComponent setBackground(JComponent comp, Color c) {
+            comp.setOpaque(true);
+            comp.setBackground(c);
+            return comp;
+        }
+
+        /** Scroll a text area to display a given position near the middle of the visible area. */
+        private void scroll(final JTextArea t, final int pos) {
+            // Using invokeLater appears to give text a chance to sort itself out
+            // before the scroll happens; otherwise scrollRectToVisible doesn't work.
+            // Maybe there's a better way to sync with the text...
+            EventQueue.invokeLater(new Runnable() {
+                public void run() {
+                    try {
+                        Rectangle r = t.modelToView(pos);
+                        JScrollPane p = (JScrollPane) SwingUtilities.getAncestorOfClass(JScrollPane.class, t);
+                        r.y = Math.max(0, r.y - p.getHeight() * 2 / 5);
+                        r.height += p.getHeight() * 4 / 5;
+                        t.scrollRectToVisible(r);
+                    } catch (BadLocationException ignore) {
+                    }
+                }
+            });
+        }
+
+        private JComboBox entries;
+        private JTextField checkField;
+        private InfoPanel enclPanel;
+        private InfoPanel selfPanel;
+        private JTextArea body;
+        private JTextField statusText;
+
+        private Color selfColor = new Color(0.f, 1.f, 0.f, 0.2f); // 20% green
+        private Color enclColor = new Color(1.f, 0.f, 0.f, 0.2f); // 20% red
+
+        /** Panel to display an Info object. */
+        private class InfoPanel extends JPanel {
+            InfoPanel() {
+                add(tagName = createTextField(20));
+                add(new JLabel("start:"));
+                add(addListener(start = createTextField(6)));
+                add(new JLabel("pos:"));
+                add(addListener(pos = createTextField(6)));
+                add(new JLabel("end:"));
+                add(addListener(end = createTextField(6)));
+            }
+
+            void setInfo(Info info) {
+                this.info = info;
+                tagName.setText(getTagName(info.tag));
+                start.setText(String.valueOf(info.start));
+                pos.setText(String.valueOf(info.pos));
+                end.setText(String.valueOf(info.end));
+            }
+
+            JTextField addListener(final JTextField f) {
+                f.addMouseListener(new MouseAdapter() {
+                    @Override
+                    public void mouseClicked(MouseEvent e) {
+                        body.setCaretPosition(Integer.valueOf(f.getText()));
+                        body.getCaret().setVisible(true);
+                    }
+                });
+                return f;
+            }
+
+            Info info;
+            JTextField tagName;
+            JTextField start;
+            JTextField pos;
+            JTextField end;
+        }
+
+        /** Object to record information about an error to be displayed. */
+        private class Entry {
+            Entry(JavaFileObject file, String check, Info encl, Info self) {
+                this.file = file;
+                this.check = check;
+                this.encl = encl;
+                this.self= self;
+            }
+
+            @Override
+            public String toString() {
+                return file.getName() + " " + check + " " + getMinPos(encl, self);
+            }
+
+            final JavaFileObject file;
+            final String check;
+            final Info encl;
+            final Info self;
+        }
+    }
+}
+