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
return DND.DROP_COPY;
		else
			return DND.DROP_NONE;					
	}
			
	private boolean canCopyElements() {
		if (fCanCopyElements == 0) {
			fCanCopyElements= 2;
			if (fCopyRefactoring2 == null)
				fCanCopyElements= 1;
		}
		return fCanCopyElements == 2;
	}		
	
	private void handleDropCopy(final Object target, DropTargetEvent event) throws JavaModelException, InvocationTargetException, InterruptedException{
		IJavaElement[] javaElements= ReorgUtils.getJavaElements(fElements);
		IResource[] resources= ReorgUtils.getResources(fElements);
		ReorgCopyStarter starter= null;
		if (target instanceof IResource) 
			starter= ReorgCopyStarter.create(javaElements, resources, (IResource)target);
		else if (target instanceof IJavaElement)
			starter= ReorgCopyStarter.create(javaElements, resources, (IJavaElement)target);
		if (starter != null)
			starter.run(getShell());
	}
	private Shell getShell() {
		return getViewer().getControl().getShell();
	}
}