GWT error - Deferred binding result type should not be abstract (or) Rebind result must be a class

When you encounter following GWT error message

either 

'Deferred binding result type should not be abstract'

in hosted or development mode

or

'Rebind result must be a class'

upon GWT compilation

then mostly it means that your GWT client service interface didn't extend the required marker interface 

com.google.gwt.user.client.rpc.RemoteService

So change your service from 

interface SampleService{

     ..

}

to

import com.google.gwt.user.client.rpc.RemoteService;

interface SampleService extends RemoteService {

     ..

}

Hope this helps. Thanks to this post that helped me initially.