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
}
	
	
	public void dragEnter(DropTargetEvent event) {
		clear();
		super.dragEnter(event);
	}
	
	public void dragLeave(DropTargetEvent event) {
		clear();
		super.dragLeave(event);
	}
	
	private void clear() {
		fElements= null;
		fSelection= null;
		fMoveProcessor= null;
		fCanMoveElements= 0;
		fCopyRefactoring2= null;
		fCanCopyElements= 0;
	}
	
	public void validateDrop(Object target, DropTargetEvent event, int operation) {
		event.detail= DND.DROP_NONE;
		
		if (tooFast(event)) 
			return;
		
		initializeSelection();