CheckAttributedTree.java 27.1 KB
Newer Older
1
/*
J
jjg 已提交
2
 * Copyright (c) 2010, 2012, Oracle and/or its affiliates. All rights reserved.
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70
 * 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 com.sun.source.util.TaskEvent;
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 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 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.util.ArrayList;
import java.util.List;
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.source.util.TaskListener;
import com.sun.tools.javac.api.JavacTool;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Type;
J
jjg 已提交
71
import com.sun.tools.javac.tree.EndPosTable;
72 73 74 75 76 77 78 79 80 81 82 83
import com.sun.tools.javac.tree.JCTree;
import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
import com.sun.tools.javac.tree.JCTree.JCImport;
import com.sun.tools.javac.tree.TreeInfo;
import com.sun.tools.javac.tree.TreeScanner;
import com.sun.tools.javac.util.Pair;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import javax.lang.model.element.Element;

84 85
import static com.sun.tools.javac.tree.JCTree.Tag.*;

86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252
/**
 * 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 6970584
 * @summary assorted position errors in compiler syntax trees
 * @run main CheckAttributedTree -q -r -et ERRONEOUS .
 */
public class CheckAttributedTree {
    /**
     * 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) {
        String testSrc = System.getProperty("test.src");
        File baseDir = (testSrc == null) ? null : new File(testSrc);
        boolean ok = new CheckAttributedTree().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) {
        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()) {
                    if (d == null)
                        throw new Error("cannot find TEST.ROOT");
                    d = d.getParentFile();
                }
                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);
    }

    /**
     * Print command line help.
     * @param out output stream
     */
    void usage(PrintStream out) {
        out.println("Usage:");
        out.println("  java CheckAttributedTree options... files...");
        out.println("");
        out.println("where options include:");
        out.println("-q        Quiet: don't report on inapplicable files");
        out.println("-gui      Display returns in a GUI viewer");
        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++;
                NPETester p = new NPETester();
                p.test(read(file));
            } catch (AttributionException e) {
                if (!quiet) {
                    error("Error attributing " + file + "\n" + e.getMessage());
                }
            } catch (IOException e) {
                error("Error reading " + file + ": " + e);
            }
            return;
        }

        if (!quiet)
            error("File " + file + " ignored");
    }

253 254 255 256 257 258 259
    // 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);

260 261 262 263 264 265 266 267 268
    /**
     * 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
     */
    List<Pair<JCCompilationUnit, JCTree>> read(File file) throws IOException, AttributionException {
        JavacTool tool = JavacTool.create();
269
        r.errors = 0;
270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285
        Iterable<? extends JavaFileObject> files = fm.getJavaFileObjects(file);
        String[] opts = { "-XDshouldStopPolicy=ATTR", "-XDverboseCompilePolicy" };
        JavacTask task = tool.getTask(pw, fm, r, Arrays.asList(opts), null, files);
        final List<Element> analyzedElems = new ArrayList<>();
        task.setTaskListener(new TaskListener() {
            public void started(TaskEvent e) {
                if (e.getKind() == TaskEvent.Kind.ANALYZE)
                        analyzedElems.add(e.getTypeElement());
            }
            public void finished(TaskEvent e) { }
        });

        try {
            Iterable<? extends CompilationUnitTree> trees = task.parse();
            task.analyze();
            List<Pair<JCCompilationUnit, JCTree>> res = new ArrayList<>();
J
jjg 已提交
286
            //System.out.println("Try to add pairs. Elems are " + analyzedElems);
287 288 289
            for (CompilationUnitTree t : trees) {
               JCCompilationUnit cu = (JCCompilationUnit)t;
               for (JCTree def : cu.defs) {
290
                   if (def.hasTag(CLASSDEF) &&
291
                           analyzedElems.contains(((JCTree.JCClassDecl)def).sym)) {
J
jjg 已提交
292
                       //System.out.println("Adding pair...");
293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373
                       res.add(new Pair<>(cu, def));
                   }
               }
            }
            return res;
        }
        catch (Throwable t) {
            throw new AttributionException("Exception while attributing file: " + file);
        }
    }

    /**
     * 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++;
    }

    /** Number of files that have been analyzed. */
    int fileCount;
    /** Number of errors reported. */
    int errors;
    /** Flag: don't report irrelevant files. */
    boolean quiet;
    /** Flag: show errors in GUI viewer. */
    boolean gui;
    /** The GUI viewer for errors. */
    Viewer viewer;
    /** Flag: report files as they are processed. */
    boolean verbose;
    /** Option: encoding for test files. */
    String encoding;
    /** 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>();
    /** Utility class for trees */
    TreeUtil treeUtil = new TreeUtil();

    /**
     * Main class for testing assertions concerning types/symbol
     * left uninitialized after attribution
     */
    private class NPETester extends TreeScanner {
        void test(List<Pair<JCCompilationUnit, JCTree>> trees) {
            for (Pair<JCCompilationUnit, JCTree> p : trees) {
                sourcefile = p.fst.sourcefile;
                endPosTable = p.fst.endPositions;
                encl = new Info(p.snd, endPosTable);
                p.snd.accept(this);
            }
        }

        @Override
        public void scan(JCTree tree) {
            if (tree == null ||
                    excludeTags.contains(treeUtil.nameFromTag(tree.getTag()))) {
                return;
            }

            Info self = new Info(tree, endPosTable);
            check(!mandatoryType(tree) ||
                    (tree.type != null &&
                    checkFields(tree)),
                    "'null' found in tree ",
                    self);

            Info prevEncl = encl;
            encl = self;
            tree.accept(this);
            encl = prevEncl;
        }

        private boolean mandatoryType(JCTree that) {
            return that instanceof JCTree.JCExpression ||
374 375 376
                    that.hasTag(VARDEF) ||
                    that.hasTag(METHODDEF) ||
                    that.hasTag(CLASSDEF);
377 378
        }

379
        private final List<String> excludedFields = Arrays.asList("varargsElement", "targetType");
380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419

        void check(boolean ok, String label, Info self) {
            if (!ok) {
                if (gui) {
                    if (viewer == null)
                        viewer = new Viewer();
                    viewer.addEntry(sourcefile, label, encl, self);
                }
                error(label + self.toString() + " encl: " + encl.toString() + " in file: " + sourcefile + "  " + self.tree);
            }
        }

        boolean checkFields(JCTree t) {
            List<Field> fieldsToCheck = treeUtil.getFieldsOfType(t,
                    excludedFields,
                    Symbol.class,
                    Type.class);
            for (Field f : fieldsToCheck) {
                try {
                    if (f.get(t) == null) {
                        return false;
                    }
                }
                catch (IllegalAccessException e) {
                    System.err.println("Cannot read field: " + f);
                    //swallow it
                }
            }
            return true;
        }

        @Override
        public void visitImport(JCImport tree) { }

        @Override
        public void visitTopLevel(JCCompilationUnit tree) {
            scan(tree.defs);
        }

        JavaFileObject sourcefile;
K
ksrini 已提交
420
        EndPosTable endPosTable;
421 422 423 424 425 426 427 428 429
        Info encl;
    }

    /**
     * Utility class providing easy access to position and other info for a tree node.
     */
    private class Info {
        Info() {
            tree = null;
430
            tag = ERRONEOUS;
431 432 433 434 435
            start = 0;
            pos = 0;
            end = Integer.MAX_VALUE;
        }

K
ksrini 已提交
436
        Info(JCTree tree, EndPosTable endPosTable) {
437 438 439 440 441 442 443 444 445 446 447 448 449
            this.tree = tree;
            tag = tree.getTag();
            start = TreeInfo.getStartPos(tree);
            pos = tree.pos;
            end = TreeInfo.getEndPos(tree, endPosTable);
        }

        @Override
        public String toString() {
            return treeUtil.nameFromTag(tree.getTag()) + "[start:" + start + ",pos:" + pos + ",end:" + end + "]";
        }

        final JCTree tree;
450
        final JCTree.Tag tag;
451 452 453 454 455 456 457 458 459
        final int start;
        final int pos;
        final int end;
    }

    /**
     * Names for tree tags.
     */
    private static class TreeUtil {
460 461
        String nameFromTag(JCTree.Tag tag) {
            String name = tag.name();
462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757
            return (name == null) ? "??" : name;
        }

        List<Field> getFieldsOfType(JCTree t, List<String> excludeNames, Class<?>... types) {
            List<Field> buf = new ArrayList<Field>();
            for (Field f : t.getClass().getDeclaredFields()) {
                if (!excludeNames.contains(f.getName())) {
                    for (Class<?> type : types) {
                        if (type.isAssignableFrom(f.getType())) {
                            f.setAccessible(true);
                            buf.add(f);
                            break;
                        }
                    }
                }
            }
            return buf;
        }
    }

    /**
     * Thrown when errors are found parsing a java file.
     */
    private static class ParseException extends Exception {
        ParseException(String msg) {
            super(msg);
        }
    }

    private static class AttributionException extends Exception {
        AttributionException(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(treeUtil.nameFromTag(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;
        }
    }
}