Deferred.callback(anotherDeferred)

[etrepum]

This was discussed on #tmlabs today.  The current (as of today) behavior is to assert that the user 
doesn't do this, and force them to use maybeDeferred or Deferred.chain themselves.

Is this really necessary?  I think that implicit handling of this would work fine most of the time.  
Here's a trivial example of how to behave badly:

    from twisted.internet.defer import succeed
    def print_(v): print v
    succeed(succeed(1)).addCallback(print_)

[exarkun]

The general concensus is that this is almost always an error on the programmer's
part.  Making it raise an exception saves more time than it costs.

Does anyone else disagree?

[glyph]

I guess not.