Program: 124086
Project: 124086
Buggy source:
public void initialDrop(){
  int operations=DND.DROP_MOVE | DND.DROP_COPY | DND.DROP_DEFAULT;
  DropTarget target=new DropTarget(contextComposite,operations);
  final LocalSelectionTransfer transfer=LocalSelectionTransfer.getTransfer();
  target.setTransfer(new Transfer[]{transfer});
  target.addDropListener(new DropTargetListener(){
    public void dropAccept(    DropTargetEvent event){
    }
    public void drop(    DropTargetEvent event){
      if (transfer.isSupportedType(event.currentDataType)) {
        ISelection selection=transfer.getSelection();
        if (selection instanceof TreeSelection) {
          Object[] objects=((TreeSelection)selection).toArray();
          List<Object> asList=Arrays.asList(objects);
          boolean created=false;
          for (          Object obj : objects) {
            if (obj instanceof RepositoryNode) {
              RepositoryNode sourceNode=(RepositoryNode)obj;
              Item item=sourceNode.getObject().getProperty().getItem();
              if (item instanceof ContextItem) {
                ContextItem contextItem=(ContextItem)item;
                EList context=contextItem.getContext();
                Set<String> contextSet=new HashSet<String>();
                Iterator iterator=context.iterator();
                while (iterator.hasNext()) {
                  Object repositoryObject=iterator.next();
                  if (repositoryObject instanceof ContextTypeImpl) {
                    EList contextParameters=((ContextTypeImpl)repositoryObject).getContextParameter();
                    Iterator contextParas=contextParameters.iterator();
                    while (contextParas.hasNext()) {
                      ContextParameterTypeImpl contextParameterType=(ContextParameterTypeImpl)contextParas.next();
                      String name=contextParameterType.getName();
                      contextSet.add(name);
                    }
                  }
                }
                IEditorInput editorInput=part.getEditorInput();
                if (editorInput instanceof JobEditorInput) {
                  JobEditorInput jobInput=(JobEditorInput)editorInput;
                  IProcess2 process=jobInput.getLoadedProcess();
                  IContextManager contextManager=process.getContextManager();
                  Set<String> addedContext=ConnectionContextHelper.checkAndAddContextVariables(contextItem,contextSet,contextManager,false);
                  if (addedContext != null && addedContext.size() > 0) {
                    ConnectionContextHelper.addContextVarForJob(process,contextItem,contextSet);
                    created=true;
                  }
                }
              }
            }
          }
          if (created) {
            RepositoryPlugin.getDefault().getDesignerCoreService().switchToCurContextsView();
          }
        }
      }
    }
    public void dragOver(    DropTargetEvent event){
      if (transfer.isSupportedType(event.currentDataType)) {
        IEditorInput editorInput=part.getEditorInput();
        if (!(editorInput instanceof JobEditorInput)) {
          event.detail=DND.DROP_NONE;
        }
 else {
          ISelection selection=transfer.getSelection();
          if (selection instanceof TreeSelection) {
            Object[] objects=((TreeSelection)selection).toArray();
            for (            Object obj : objects) {
              if (obj instanceof RepositoryNode) {
                RepositoryNode sourceNode=(RepositoryNode)obj;
                Item item=sourceNode.getObject().getProperty().getItem();
                if (!(item instanceof ContextItem)) {
                  event.detail=DND.DROP_NONE;
                }
              }
            }
          }
        }
      }
    }
    public void dragOperationChanged(    DropTargetEvent event){
    }
    public void dragLeave(    DropTargetEvent event){
    }
    public void dragEnter(    DropTargetEvent event){
      if (event.detail == DND.DROP_DEFAULT) {
        if ((event.operations & DND.DROP_COPY) != 0) {
          event.detail=DND.DROP_COPY;
        }
 else {
          event.detail=DND.DROP_NONE;
        }
      }
      for (int i=0; i < event.dataTypes.length; i++) {
        if (transfer.isSupportedType(event.dataTypes[i])) {
          event.currentDataType=event.dataTypes[i];
          if (event.detail != DND.DROP_COPY) {
            event.detail=DND.DROP_NONE;
          }
          break;
        }
      }
    }
  }
);
}

Fixed version (ground truth):
public void initialDrop(){
  int operations=DND.DROP_MOVE | DND.DROP_COPY | DND.DROP_DEFAULT;
  DropTarget target=new DropTarget(contextComposite,operations);
  final LocalSelectionTransfer transfer=LocalSelectionTransfer.getTransfer();
  target.setTransfer(new Transfer[]{transfer});
  target.addDropListener(new DropTargetListener(){
    public void dropAccept(    DropTargetEvent event){
    }
    public void drop(    DropTargetEvent event){
      if (transfer.isSupportedType(event.currentDataType)) {
        ISelection selection=transfer.getSelection();
        if (selection instanceof TreeSelection) {
          Object[] objects=((TreeSelection)selection).toArray();
          List<Object> asList=Arrays.asList(objects);
          boolean created=false;
          for (          Object obj : objects) {
            if (obj instanceof RepositoryNode) {
              RepositoryNode sourceNode=(RepositoryNode)obj;
              Item item=sourceNode.getObject().getProperty().getItem();
              if (item instanceof ContextItem) {
                ContextItem contextItem=(ContextItem)item;
                EList context=contextItem.getContext();
                Set<String> contextSet=new HashSet<String>();
                Iterator iterator=context.iterator();
                while (iterator.hasNext()) {
                  Object repositoryObject=iterator.next();
                  if (repositoryObject instanceof ContextTypeImpl) {
                    EList contextParameters=((ContextTypeImpl)repositoryObject).getContextParameter();
                    Iterator contextParas=contextParameters.iterator();
                    while (contextParas.hasNext()) {
                      ContextParameterTypeImpl contextParameterType=(ContextParameterTypeImpl)contextParas.next();
                      String name=contextParameterType.getName();
                      contextSet.add(name);
                    }
                  }
                }
                IEditorInput editorInput=part.getEditorInput();
                if (editorInput instanceof JobEditorInput) {
                  JobEditorInput jobInput=(JobEditorInput)editorInput;
                  IProcess2 process=jobInput.getLoadedProcess();
                  IContextManager contextManager=process.getContextManager();
                  List<IContext> listContext=contextManager.getListContext();
                  if (!ConnectionContextHelper.containsVariable(contextManager)) {
                    ConnectionContextHelper.addContextVarForJob(process,contextItem,contextManager);
                    created=true;
                  }
 else {
                    Set<String> addedContext=ConnectionContextHelper.checkAndAddContextVariables(contextItem,contextSet,contextManager,false);
                    if (addedContext != null && addedContext.size() > 0) {
                      ConnectionContextHelper.addContextVarForJob(process,contextItem,contextSet);
                      created=true;
                    }
                  }
                }
              }
            }
          }
          if (created) {
            RepositoryPlugin.getDefault().getDesignerCoreService().switchToCurContextsView();
          }
        }
      }
    }
    public void dragOver(    DropTargetEvent event){
      if (transfer.isSupportedType(event.currentDataType)) {
        IEditorInput editorInput=part.getEditorInput();
        if (!(editorInput instanceof JobEditorInput)) {
          event.detail=DND.DROP_NONE;
        }
 else {
          ISelection selection=transfer.getSelection();
          if (selection instanceof TreeSelection) {
            Object[] objects=((TreeSelection)selection).toArray();
            for (            Object obj : objects) {
              if (obj instanceof RepositoryNode) {
                RepositoryNode sourceNode=(RepositoryNode)obj;
                Item item=sourceNode.getObject().getProperty().getItem();
                if (!(item instanceof ContextItem)) {
                  event.detail=DND.DROP_NONE;
                }
              }
            }
          }
        }
      }
    }
    public void dragOperationChanged(    DropTargetEvent event){
    }
    public void dragLeave(    DropTargetEvent event){
    }
    public void dragEnter(    DropTargetEvent event){
      if (event.detail == DND.DROP_DEFAULT) {
        if ((event.operations & DND.DROP_COPY) != 0) {
          event.detail=DND.DROP_COPY;
        }
 else {
          event.detail=DND.DROP_NONE;
        }
      }
      for (int i=0; i < event.dataTypes.length; i++) {
        if (transfer.isSupportedType(event.dataTypes[i])) {
          event.currentDataType=event.dataTypes[i];
          if (event.detail != DND.DROP_COPY) {
            event.detail=DND.DROP_NONE;
          }
          break;
        }
      }
    }
  }
);
}