Program: 31522
Project: 31522
Buggy source:
public void produce() throws IOException {
  TreeClassifier c=new RootAndLeavesClassifier(src,dst,matcher);
  TIntIntMap mappingIds=new TIntIntHashMap();
  int uId=1;
  int mId=1;
  TagIndex ltags=new TagIndex();
  for (  ITree t : src.getRoot().getTrees()) {
    if (c.getSrcMvTrees().contains(t)) {
      mappingIds.put(mappings.getDst(t).getId(),mId);
      ltags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      ltags.addTags(t.getPos(),String.format(SRC_MV_SPAN,"String_Node_Str",mId++,tooltip(src,t)),t.getEndPos(),END_SPAN);
    }
    if (c.getSrcUpdTrees().contains(t)) {
      mappingIds.put(mappings.getDst(t).getId(),mId);
      ltags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      ltags.addTags(t.getPos(),String.format(SRC_MV_SPAN,"String_Node_Str",mId++,tooltip(src,t)),t.getEndPos(),END_SPAN);
      List<int[]> hunks=StringAlgorithms.hunks(t.getLabel(),mappings.getDst(t).getLabel());
      for (      int[] hunk : hunks)       ltags.addTags(t.getPos() + hunk[0],UPD_SPAN,t.getPos() + hunk[1],END_SPAN);
    }
    if (c.getSrcDelTrees().contains(t)) {
      ltags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      ltags.addTags(t.getPos(),String.format(ADD_DEL_SPAN,"String_Node_Str",tooltip(src,t)),t.getEndPos(),END_SPAN);
    }
  }
  TagIndex rtags=new TagIndex();
  for (  ITree t : dst.getRoot().getTrees()) {
    if (c.getDstMvTrees().contains(t)) {
      int dId=mappingIds.get(t.getId());
      rtags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      rtags.addTags(t.getPos(),String.format(DST_MV_SPAN,"String_Node_Str",dId,tooltip(dst,t)),t.getEndPos(),END_SPAN);
    }
    if (c.getDstUpdTrees().contains(t)) {
      int dId=mappingIds.get(t.getId());
      rtags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      rtags.addTags(t.getPos(),String.format(DST_MV_SPAN,"String_Node_Str",dId,tooltip(dst,t)),t.getEndPos(),END_SPAN);
      List<int[]> hunks=StringAlgorithms.hunks(mappings.getSrc(t).getLabel(),t.getLabel());
      for (      int[] hunk : hunks)       rtags.addTags(t.getPos() + hunk[2],UPD_SPAN,t.getPos() + hunk[3],END_SPAN);
    }
    if (c.getDstAddTrees().contains(t)) {
      rtags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      rtags.addTags(t.getPos(),String.format(ADD_DEL_SPAN,"String_Node_Str",tooltip(dst,t)),t.getEndPos(),END_SPAN);
    }
  }
  StringWriter w1=new StringWriter();
  BufferedReader r=new BufferedReader(new FileReader(fSrc));
  int cursor=0;
  while (r.ready()) {
    char cr=(char)r.read();
    w1.append(ltags.getEndTags(cursor));
    w1.append(ltags.getStartTags(cursor));
    append(cr,w1);
    cursor++;
  }
  w1.append(ltags.getEndTags(cursor));
  r.close();
  srcDiff=w1.toString();
  StringWriter w2=new StringWriter();
  r=new BufferedReader(new FileReader(fDst));
  cursor=0;
  while (r.ready()) {
    char cr=(char)r.read();
    w2.append(rtags.getEndTags(cursor));
    w2.append(rtags.getStartTags(cursor));
    append(cr,w2);
    cursor++;
  }
  w2.append(rtags.getEndTags(cursor));
  r.close();
  dstDiff=w2.toString();
}

Fixed version (ground truth):
public void produce() throws IOException {
  TreeClassifier c=new RootAndLeavesClassifier(src,dst,matcher);
  TIntIntMap mappingIds=new TIntIntHashMap();
  int uId=1;
  int mId=1;
  TagIndex ltags=new TagIndex();
  for (  ITree t : src.getRoot().getTrees()) {
    if (c.getSrcMvTrees().contains(t)) {
      mappingIds.put(mappings.getDst(t).getId(),mId);
      ltags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      ltags.addTags(t.getPos(),String.format(SRC_MV_SPAN,"String_Node_Str",mId++,tooltip(src,t)),t.getEndPos(),END_SPAN);
    }
    if (c.getSrcUpdTrees().contains(t)) {
      mappingIds.put(mappings.getDst(t).getId(),mId);
      ltags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      ltags.addTags(t.getPos(),String.format(SRC_MV_SPAN,"String_Node_Str",mId++,tooltip(src,t)),t.getEndPos(),END_SPAN);
      List<int[]> hunks=StringAlgorithms.hunks(t.getLabel(),mappings.getDst(t).getLabel());
      for (      int[] hunk : hunks)       ltags.addTags(t.getPos() + hunk[0],UPD_SPAN,t.getPos() + hunk[1],END_SPAN);
    }
    if (c.getSrcDelTrees().contains(t)) {
      ltags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      ltags.addTags(t.getPos(),String.format(ADD_DEL_SPAN,"String_Node_Str",tooltip(src,t)),t.getEndPos(),END_SPAN);
    }
  }
  TagIndex rtags=new TagIndex();
  for (  ITree t : dst.getRoot().getTrees()) {
    if (c.getDstMvTrees().contains(t)) {
      int dId=mappingIds.get(t.getId());
      rtags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      rtags.addTags(t.getPos(),String.format(DST_MV_SPAN,"String_Node_Str",dId,tooltip(dst,t)),t.getEndPos(),END_SPAN);
    }
    if (c.getDstUpdTrees().contains(t)) {
      int dId=mappingIds.get(t.getId());
      rtags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      rtags.addTags(t.getPos(),String.format(DST_MV_SPAN,"String_Node_Str",dId,tooltip(dst,t)),t.getEndPos(),END_SPAN);
      List<int[]> hunks=StringAlgorithms.hunks(mappings.getSrc(t).getLabel(),t.getLabel());
      for (      int[] hunk : hunks)       rtags.addTags(t.getPos() + hunk[2],UPD_SPAN,t.getPos() + hunk[3],END_SPAN);
    }
    if (c.getDstAddTrees().contains(t)) {
      rtags.addStartTag(t.getPos(),String.format(ID_SPAN,uId++));
      rtags.addTags(t.getPos(),String.format(ADD_DEL_SPAN,"String_Node_Str",tooltip(dst,t)),t.getEndPos(),END_SPAN);
    }
  }
  StringWriter w1=new StringWriter();
  BufferedReader r=Files.newBufferedReader(fSrc.toPath(),Charset.forName("String_Node_Str"));
  int cursor=0;
  while (r.ready()) {
    char cr=(char)r.read();
    w1.append(ltags.getEndTags(cursor));
    w1.append(ltags.getStartTags(cursor));
    append(cr,w1);
    cursor++;
  }
  w1.append(ltags.getEndTags(cursor));
  r.close();
  srcDiff=w1.toString();
  StringWriter w2=new StringWriter();
  r=Files.newBufferedReader(fDst.toPath(),Charset.forName("String_Node_Str"));
  cursor=0;
  while (r.ready()) {
    char cr=(char)r.read();
    w2.append(rtags.getEndTags(cursor));
    w2.append(rtags.getStartTags(cursor));
    append(cr,w2);
    cursor++;
  }
  w2.append(rtags.getEndTags(cursor));
  r.close();
  dstDiff=w2.toString();
}