3 Problems caused by unimplemented Mercury features

1. How can I avoid getting a compile-time error when I try to fill in a partially instantiated data structure?
   

   At the moment, you can create a partially instantiated data structure, but you can’t fill in the holes. The reason is that the code that does the filling in must temporarily alias two variables together, and the current mode checker does not allow this. This limitation will go away in the future.