[issue38660] Checking if two regexes are equal should test if they are functionally equivalent

[Serhiy Storchaka]

Serhiy Storchaka <storchaka+cpython at gmail.com> added the comment:

These two regexes are not the same.

>>> re.compile('([-_.a-zA-Z0-9]+)').match('ä')
>>> re.compile(r'([-\w.]+)').match('ä')
<re.Match object; span=(0, 1), match='ä'>

As Ammar said checking that two regexes always matches the same is very difficult problem. It is the problem of determining if two programs are the same.

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nosy: +serhiy.storchaka

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