Bug 63155 [Refactoring] no user feedback when error during implicit refactoring triggered by drag'n'drop
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/SelectionTransferDropAdapter.java
try {
			switch(operation) {
				case DND.DROP_DEFAULT:	event.detail= handleValidateDefault(target, event); break;
				case DND.DROP_COPY: 		event.detail= handleValidateCopy(target, event); break;
				case DND.DROP_MOVE: 		event.detail= handleValidateMove(target, event); break;
				case DND.DROP_LINK: 			event.detail= handleValidateLink(target, event); break;
			}
		} catch (JavaModelException e){
			ExceptionHandler.handle(e, PackagesMessages.getString("SelectionTransferDropAdapter.error.title"), PackagesMessages.getString("SelectionTransferDropAdapter.error.message")); 
			event.detail= DND.DROP_NONE;
		}	
	}
	protected void initializeSelection(){
		if (fElements != null)
			return;
		ISelection s= LocalSelectionTransfer.getInstance().getSelection();
		if (!(s instanceof IStructuredSelection))
			return;
		fSelection= s;	
		fElements= ((IStructuredSelection)s).toList();
	}
	
	protected ISelection getSelection(){
		return fSelection;
	}
	
	private boolean tooFast(DropTargetEvent event) {
		return Math.abs(LocalSelectionTransfer.getInstance().getSelectionSetTime() - (event.time & 0xFFFFFFFFL)) < DROP_TIME_DIFF_TRESHOLD;
	}	
	public void drop(Object target, DropTargetEvent event) {