Step to reproduce:

$ echo 'file("/some/file")' | python `which 2to3` -

(replace python with whichever python executable version you wish to
use, e.g. ~/python-trunk/python or /usr/local/bin/python3.2 )

Expected result:
Anything referring to the fact that the "file" type no longer exists in
python 3.x, whether it be a warning or a refactoring.

Actual result:
RefactoringTool: No files need to be modified.

Just a report for now, I don't have the time to write a patch.

Patch attached. Unit test and documentation included.

COMMITMSG:

Adds a new fixer to lib2to3 which replaces the deprecated builtin "file" with "open".

Woops. Removed the extra comments. Updated patch attached.

Unfortunately this patch would also replace legitimate uses of a "file" function.

I thought the whole point was that file[1] was removed in 3.0[2]? Or, are you saying that if somebody overloaded file with def file(...)? If that is the case would it be reasonable to check like this?

>>> file in list(__builtins__.__dict__.values())
True
>>> def file():
...     pass
... 
>>> file in list(__builtins__.__dict__.values())
False
>>> 


[1] - http://docs.python.org/library/functions.html?highlight=file#file
[2] - http://docs.python.org/3.1/whatsnew/3.0.html#builtins

Yes, the idea was that it doesn't seem outlandish for someone to do:
def file(something):
    do_stuff()

You can use lib2to3.fixer_util.is_probably_builtin for this... modified the patch and attached.