> + (when (or (function-get function 'pure)
> + (function-get function 'side-effect-free))
> + (insert "\nThis function does not change the match data."))
Wouldn't it be more useful to say it doesn't have side-effects (which
would obviously imply it doesn't change the match-data, along with all
other global state)?
I'd prefer to mention the match data explicitly, because users might not be aware that they are part of the global state. Maybe something like "This function does not (access|change) global state, including the match data" (where "access" can be used for the pure ones).