cascading column drop to index predicates

Hey Tom,

With regards to our previous conversation about dropping columns now 
properly dropping indexes that contain predicates that reference that 
column,  I now find it a bit disconcerting that such indexes are 
automatically removed when the column is dropped, instead of requiring a 
CASCADE.

The thing is, if you drop a column that is used in a normal index, yes 
the index is now useless - drop it.

However, since you can have (and I have) indexes like this:

CREATE INDEX asdf ON table (a, b, c) WHERE d IS NOT NULL;

If I drop column d, there is no way I want that index to just disappear!

This has already caught me out...

Can we change it to requiring a CASCADE?  Is that a good idea?

Chris