bug#64128: regexp parser zero-width assertion bugs

[Stefan Monnier]

>> If I understand things correctly, this would cause "\b*c" to be treated like 
>> "\b\*c".
> Actually it already works that way. What the patch does, is preventing
> AB\b*C from being treated as \(?:AB\b\)*C but as AB\b\*C instead, which
> I think we can all agree is less wrong.

Hmm... maybe it's less wrong, but I'd rather make it behave like
AB\(\b\)*C, which is, I'd argue, even less wrong.

Or maybe make it signal an error: I can't imagine that the current
behavior is used by very much code at all, seeing how it's so
seriously non-intuitive.


        Stefan