bug#6388: Should not match data be set on misses?

[Stefan Monnier]

>> The main obstacle to such a change are:
>> - it breaks some code.
> Aka it makes some bugs (bad assumptions) surface. That is not always bad.

I really meant bugs, as in: the code consciously takes advantage of
current behavior.  Those assumptions are only bad if we define them
that way.

> Yes, that is true. However the current behavior probably wastes a lot
> of time for those unaware of it.

Just like with programming with monitors where you're taught "always do
the wait within a `while' loop", regexp-patching should always take
place within a `if' or equivalent,


        Stefan