bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?

[Stefan Monnier]

>>> There are also some functions declared 'pure' that appear to have side
>>> effects: kbd, package-get-version
>> Which side-effects are you thinking of?
> They both clobber the match data.

It's not a problem w.r.t optimizing pure functions, tho: those functions
don't promise to modify the match data, so it's OK to replace calls to
them with their return value.

But yes, it's a problem because `C-h o kbd RET` says explicitly that it
doesn't change the match data :-(


        Stefan