[Guido]
... It needs to add 'None' as an alternative to all other places where currently NAME occurs.
Fudge. None makes no sense anywhere in, e.g.,
dotted_name: NAME ('.' NAME)*
or
global_stmt: 'global' NAME (',' NAME)*but I suppose it has to be allowed for in 2.3 anyway else an existing
Yes, that's (alas) the point.
import None.None.None as Nonewould yield a SyntaxError instead of a warning.
More realistically,
def foo(a, None=None): if a is None: ...
I found 4 examples of this in Zope3 alone, and MAL has some too.
Note too that we can't change the generated code at all for 2.3 unless under the control of a new future statement, else existing None-abusing code could break.
A future statement makes no sense for this, so I guess all we can do in 2.3 is warn about use of None in all contexts except in expressions.
This is really too bad -- I wish we could decide to just break code (since it's a clean break) but apparently that's unacceptable to the users.
--Guido van Rossum (home page: http://www.python.org/~guido/)