Program: 29432
Project: 29432
Buggy source:
/** 
 * A helper method that compare two   {@code HtmlTagEntry}s. 
 */
public static boolean matchOrError(@Nullable HtmlTagEntry openTag,@Nullable HtmlTagEntry closeTag,ErrorReporter errorReporter){
  if (openTag == null && closeTag == null) {
    return true;
  }
  if (openTag == null && closeTag != null) {
    errorReporter.report(closeTag.getSourceLocation(),UNEXPECTED_CLOSE_TAG);
    return false;
  }
  if (openTag != null && closeTag == null) {
    errorReporter.report(openTag.getSourceLocation(),OPEN_TAG_NOT_CLOSED);
    return false;
  }
  if (openTag.hasTagName() != closeTag.hasTagName()) {
    boolean matchCommonPrefix=false;
    if (openTag.hasTagName()) {
      TagName openTagName=openTag.getTagName();
      if (closeTag.getBranches().hasCommonPrefix(openTagName)) {
        closeTag.getBranches().popAllBranches();
        matchCommonPrefix=true;
        if (!closeTag.getBranches().isEmpty()) {
          matchCommonPrefix=false;
          errorReporter.report(closeTag.getSourceLocation(),UNEXPECTED_CLOSE_TAG_WITH_EXPECTATION,openTagName.getStaticTagNameAsLowerCase().get());
        }
      }
 else {
        errorReporter.report(openTagName.getTagLocation(),OPEN_TAG_NOT_CLOSED);
      }
    }
 else {
      TagName closeTagName=closeTag.getTagName();
      if (openTag.getBranches().hasCommonPrefix(closeTagName)) {
        openTag.getBranches().popAllBranches();
        matchCommonPrefix=true;
        if (!openTag.getBranches().isEmpty()) {
          matchCommonPrefix=false;
          errorReporter.report(openTag.getSourceLocation(),OPEN_TAG_NOT_CLOSED);
        }
      }
 else {
        errorReporter.report(closeTagName.getTagLocation(),UNEXPECTED_CLOSE_TAG);
      }
    }
    return matchCommonPrefix;
  }
  if (openTag.hasTagName()) {
    return matchOrError(openTag.getTagName(),closeTag.getTagName(),errorReporter);
  }
 else {
    List<ConditionalBranches.ConditionalBranch> openBranches=openTag.getBranches().getBranches();
    List<ConditionalBranches.ConditionalBranch> closeBranches=closeTag.getBranches().getBranches();
    SourceLocation location=closeTag.getSourceLocation();
    if (openBranches.size() != closeBranches.size()) {
      errorReporter.report(location,MISMATCH_TAG);
      return false;
    }
    for (int i=0; i < openBranches.size(); ++i) {
      ConditionalBranches.ConditionalBranch openBranch=openBranches.get(i);
      ConditionalBranches.ConditionalBranch closeBranch=closeBranches.get(i);
      if (!openBranch.condition().equals(closeBranch.condition())) {
        errorReporter.report(location,MISMATCH_TAG);
        return false;
      }
      ArrayDeque<HtmlTagEntry> openStack=openBranch.deque();
      ArrayDeque<HtmlTagEntry> closeQueue=closeBranch.deque();
      while (!openStack.isEmpty() && !closeQueue.isEmpty()) {
        if (!closeQueue.peekFirst().isDefinitelyOptional() && openStack.peekFirst().isDefinitelyOptional()) {
          openStack.pollFirst();
          continue;
        }
        if (!matchOrError(openStack.pollFirst(),closeQueue.pollFirst(),errorReporter)) {
          return false;
        }
      }
      if (openStack.isEmpty() && closeQueue.isEmpty()) {
        continue;
      }
 else       if (openStack.isEmpty()) {
        errorReporter.report(closeQueue.pollFirst().getSourceLocation(),UNEXPECTED_CLOSE_TAG);
        return false;
      }
 else {
        errorReporter.report(openStack.pollFirst().getSourceLocation(),OPEN_TAG_NOT_CLOSED);
        return false;
      }
    }
    return true;
  }
}

Fixed version (ground truth):
/** 
 * A helper method that compare two   {@code HtmlTagEntry}s. 
 */
public static boolean matchOrError(@Nullable HtmlTagEntry openTag,@Nullable HtmlTagEntry closeTag,ErrorReporter errorReporter){
  if (openTag == null && closeTag == null) {
    return true;
  }
  if (openTag == null && closeTag != null) {
    errorReporter.report(closeTag.getSourceLocation(),UNEXPECTED_CLOSE_TAG);
    return false;
  }
  if (openTag != null && closeTag == null) {
    errorReporter.report(openTag.getSourceLocation(),OPEN_TAG_NOT_CLOSED);
    return false;
  }
  if (openTag.hasTagName() != closeTag.hasTagName()) {
    boolean matchCommonPrefix=false;
    if (openTag.hasTagName()) {
      TagName openTagName=openTag.getTagName();
      if (closeTag.getBranches().hasCommonPrefix(openTagName)) {
        closeTag.getBranches().popAllBranches();
        matchCommonPrefix=true;
        if (!closeTag.getBranches().isEmpty()) {
          matchCommonPrefix=false;
          errorReporter.report(closeTag.getSourceLocation(),UNEXPECTED_CLOSE_TAG_WITH_EXPECTATION,openTagName.getStaticTagNameAsLowerCase().get());
        }
      }
 else {
        errorReporter.report(openTagName.getTagLocation(),OPEN_TAG_NOT_CLOSED);
      }
    }
 else {
      TagName closeTagName=closeTag.getTagName();
      if (openTag.getBranches().hasCommonPrefix(closeTagName)) {
        openTag.getBranches().popAllBranches();
        matchCommonPrefix=true;
        if (!openTag.getBranches().isEmpty()) {
          matchCommonPrefix=false;
          errorReporter.report(openTag.getSourceLocation(),OPEN_TAG_NOT_CLOSED);
        }
      }
 else {
        errorReporter.report(closeTagName.getTagLocation(),UNEXPECTED_CLOSE_TAG);
      }
    }
    return matchCommonPrefix;
  }
  if (openTag.hasTagName()) {
    return matchOrError(openTag.getTagName(),closeTag.getTagName(),errorReporter);
  }
 else {
    List<ConditionalBranches.ConditionalBranch> openBranches=openTag.getBranches().getBranches();
    List<ConditionalBranches.ConditionalBranch> closeBranches=closeTag.getBranches().getBranches();
    SourceLocation location=closeTag.getSourceLocation();
    if (openBranches.size() != closeBranches.size()) {
      errorReporter.report(location,MISMATCH_TAG);
      return false;
    }
    for (int i=0; i < openBranches.size(); ++i) {
      ConditionalBranches.ConditionalBranch openBranch=openBranches.get(i);
      ConditionalBranches.ConditionalBranch closeBranch=closeBranches.get(i);
      if (!openBranch.condition().equals(closeBranch.condition())) {
        errorReporter.report(location,MISMATCH_TAG);
        return false;
      }
      ArrayDeque<HtmlTagEntry> openStack=openBranch.deque();
      ArrayDeque<HtmlTagEntry> closeQueue=closeBranch.deque();
      if (!matchOrError(openStack,closeQueue,errorReporter)) {
        return false;
      }
    }
    return true;
  }
}