The attached syn.py gives a SyntaxError in 2.5a1 and
trunk.  Works fine in earlier Pythons.  Whittled down
from real-life Zope3 source.

def d(dir):
    return [fn
            for fn in os.listdir(dir)
            if fn
            if fn]

Logged In: YES 
user_id=1038590

Is including two if clauses with a single for clause really
meant to be legal?

*goes and looks at language reference*

Wow. What a strange way to write "and". . .

Logged In: YES 
user_id=31435

The whittled-down version looks ridiculous, but the original
wasn't quite such an affront to beauty :-)  It's really no
stranger than allowing pure "if" statements to nest, and it
would be more painful to contort the grammar to disallow it
(I haven't looked at the 2.5 parser, but it was very
surprising to me that it didn't allow it!).

Logged In: YES 
user_id=849994

Haha. The second "if" is seen as the beginning of a
conditional expression, so

return [fn for fn in os.listdir(dir) if fn if fn else fn]

works.

Logged In: YES 
user_id=849994

Changing

list_if: 'if' test [list_iter]

to

list_if: 'if' old_test [list_iter]

solves the problem. Conditionals must then be enclosed in
parens.

Generator expressions are also affected.

Logged In: YES 
user_id=34209

Yeah, this is definately caused by the PEP 308 patch, so I
guess the error is mine (but don't tell anyone.) Unless
someone beats me to it, I'll fix it and add a test tomorrow
(but please don't fix it without checking in some tests.)

Logged In: YES 
user_id=34209

Fixed in trunk, revision 45286.