itertools fixer fails

[VPeric]

BPO	12613
Nosy	@benjaminp, @merwok, @meadori, @asmeurer, @akheron
Superseder	bpo-45544: Close 2to3 issues and list them here
Files	issue12613.patch: Patch against 2to3 tip

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-10-20.23:00:55.905>
created_at = <Date 2011-07-22.16:49:31.763>
labels = ['type-bug', 'expert-2to3']
title = 'itertools fixer fails'
updated_at = <Date 2021-10-20.23:00:55.905>
user = 'https://bugs.python.org/VPeric'

bugs.python.org fields:

activity = <Date 2021-10-20.23:00:55.905>
actor = 'iritkatriel'
assignee = 'none'
closed = True
closed_date = <Date 2021-10-20.23:00:55.905>
closer = 'iritkatriel'
components = ['2to3 (2.x to 3.x conversion tool)']
creation = <Date 2011-07-22.16:49:31.763>
creator = 'VPeric'
dependencies = []
files = ['22878']
hgrepos = []
issue_num = 12613
keywords = ['patch', 'needs review']
message_count = 4.0
messages = ['140897', '141836', '141893', '221605']
nosy_count = 6.0
nosy_names = ['benjamin.peterson', 'eric.araujo', 'VPeric', 'meador.inge', 'Aaron.Meurer', 'petri.lehtinen']
pr_nums = []
priority = 'high'
resolution = 'wont fix'
stage = 'resolved'
status = 'closed'
superseder = '45544'
type = 'behavior'
url = 'https://bugs.python.org/issue12613'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5']

[VPeric]

The itertools fixer (izip -> zip, among others), fails for the following code:

from itertools import izip
print msg % str(bool(symbol_swapped) and list(izip(*swap_dict).next()) or symbols)

It gets converted to:

print(msg % str(bool(symbol_swapped) and list(next(izip(*swap_dict))) or symbols))

(note how izip is still there)

I've worked aroudn this by introducing tmp = izip(...) and using that, but it'd be nice if 2to3 caught it by default.

[akheron]

A smaller snippet to reproduce:

izip().next()

This gets converted to:

    next(izip())

It seems to me that the pattern of the itertools fixer doesn't match to izip().something(), and thus this is skipped.

[meadori]

I see two problems that cause the posted test cases to fail:

1. The 'next' fixer runs before the 'itertools' fixer and strips
   out a 'power' node. This keeps the 'itertools' fixer from
   matching.

2. The 'itertools' fixer does not handle any 'trailer' nodes after
   the itertool function application it is transforming.

I have fixed both of these issues in the attached patch. Full test suite run; no regressions.

[BreamoreBoy]

The patch is small and looks clean to me. Can someone take a look with a view to committing please, thanks.