http://bugs.python.org/review/25953/diff/18873/Lib/sre_parse.py
File Lib/sre_parse.py (right):

http://bugs.python.org/review/25953/diff/18873/Lib/sre_parse.py#newcode888
Lib/sre_parse.py:888: raise error("invalid group reference %r" % index)
It would be better to use s.error(). This helper sets the pattern attribute and
the position of error. If raise an error not inside addgroup(), but before
calling it, it would be possible to set correct position.

There are other "invalid group reference" errors. They don't include index. It
should be either included in all similar errors or in no one.

http://bugs.python.org/review/25953/diff/18912/Lib/sre_parse.py
File Lib/sre_parse.py (right):

http://bugs.python.org/review/25953/diff/18912/Lib/sre_parse.py#newcode888
Lib/sre_parse.py:888: raise s.error("invalid group reference %r" % index)
The position of error points after group reference. In all other cases it points
at the start of group reference.

http://bugs.python.org/review/25953/diff/18912/Lib/test/test_re.py
File Lib/test/test_re.py (right):

http://bugs.python.org/review/25953/diff/18912/Lib/test/test_re.py#newcode189
Lib/test/test_re.py:189: self.checkTemplateError('x', r'\1', 'x', 'invalid group
reference 1')
Pass the pos argument to checkTemplateError().

http://bugs.python.org/review/25953/diff/18912/Lib/test/test_re.py#newcode202
Lib/test/test_re.py:202: re.sub('x', r'\8', '')
Use checkTemplateError().

http://bugs.python.org/review/25953/diff/18912/Lib/test/test_re.py#newcode276
Lib/test/test_re.py:276: 'invalid group reference 2')
Pass the pos argument to checkTemplateError().

http://bugs.python.org/review/25953/diff/18912/Lib/test/test_re.py#newcode563
Lib/test/test_re.py:563: self.checkTemplateError('()', r'\g<%s>' %
sre_constants.MAXGROUPS, 'xx',
Pass the pos argument to checkTemplateError().

http://bugs.python.org/review/25953/diff/18912/Lib/test/test_re.py#newcode564
Lib/test/test_re.py:564: 'invalid group reference %d' % sre_constants.MAXGROUPS,
3)
sre_constants.MAXGROUPS is too long and makes the line overflowing the limit. It
is worth to use short alias for it.

https://bugs.python.org/review/25953/diff/18912/Lib/test/test_re.py
File Lib/test/test_re.py (right):

https://bugs.python.org/review/25953/diff/18912/Lib/test/test_re.py#newcode563
Lib/test/test_re.py:563: self.checkTemplateError('()', r'\g<%s>' %
sre_constants.MAXGROUPS, 'xx',
On 2016/10/20 22:44:57, storchaka wrote:
> Pass the pos argument to checkTemplateError().

That is done on next line, as the last argument

https://bugs.python.org/review/25953/diff/18937/Lib/sre_parse.py
File Lib/sre_parse.py (right):

https://bugs.python.org/review/25953/diff/18937/Lib/sre_parse.py#newcode728
Lib/sre_parse.py:728: raise source.error("invalid group reference %r" %
condgroup,
The line is too long.

https://bugs.python.org/review/25953/diff/18937/Lib/test/test_re.py
File Lib/test/test_re.py (right):

https://bugs.python.org/review/25953/diff/18937/Lib/test/test_re.py#newcode8
Lib/test/test_re.py:8: from sre_constants import MAXGROUPS
Would be better to move this import inside the test method. If MAXGROUPS is not
defined, only one test will fail.

https://bugs.python.org/review/25953/diff/18937/Lib/test/test_re.py#newcode197
Lib/test/test_re.py:197: self.checkTemplateError('x', r'\118', 'x', 'invalid
group reference 11', 2) # r'\11' + '8'
This comment (and similar comments in following lines) now can be removed.

https://bugs.python.org/review/25953/diff/18937/Lib/test/test_re.py#newcode277
Lib/test/test_re.py:277: 'invalid group reference 2', 2)
The position is wrong. It should point at the start of group name/index (compare
with above tests), i.e. be equal to 1 here.

https://bugs.python.org/review/25953/diff/18937/Lib/test/test_re.py
File Lib/test/test_re.py (right):

https://bugs.python.org/review/25953/diff/18937/Lib/test/test_re.py#newcode277
Lib/test/test_re.py:277: 'invalid group reference 2', 2)
On 2016/10/22 14:37:00, storchaka wrote:
> The position is wrong. It should point at the start of group name/index
(compare
> with above tests), i.e. be equal to 1 here.
The above tests (lines 189-201) have position equal 2. Is that also not correct
there? Or are you referring to the lines 263-275? (but then I'm not sure why
they'd be relevant here).

https://bugs.python.org/review/25953/diff/18937/Lib/test/test_re.py
File Lib/test/test_re.py (right):

https://bugs.python.org/review/25953/diff/18937/Lib/test/test_re.py#newcode277
Lib/test/test_re.py:277: 'invalid group reference 2', 2)
On 2016/10/22 15:04:59, SilentGhost wrote:
> On 2016/10/22 14:37:00, storchaka wrote:
> > The position is wrong. It should point at the start of group name/index
> (compare
> > with above tests), i.e. be equal to 1 here.
> The above tests (lines 189-201) have position equal 2. Is that also not
correct
> there?
Yes, they are not correct too.

> Or are you referring to the lines 263-275? (but then I'm not sure why
> they'd be relevant here).
Tests at lines 263-275 have correct positions. Invalid group reference 2 starts
at position 3 in pattern r'\g<2>' and at position 1 in pattern r'\2'.