bug#60974: 30.0.50; byte-compile-preprocess mutates self evaluating forms in expanded macro bodies

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

>> > Ah, right. Theother way I could think of a fix is setq-ing `form`
>> > to a
>> > shallow copy of the original form, with only the place(s) changed.
>> > This
>> > patch tries to do that by using `pcase-let` to destructure forms.
>> 
>> Hmm... yes, that's closer.  It's pretty ugly, tho.
>> Yet it's hard to make it less ugly here because the
>> `cconv-freevars-alist` really depends on `eq` equality.
>> 
>> Maybe we should pass `cif` to `cconv--convert-function` (or maybe
>> even
>> move most of that `cconv--interactive-form-funs`-handling to that
>> function) and arrange for that function to do the
>> "non-side-effecting-equivalent-of" (setf (cadr (car bf)) form)?
>> 
>> 
>>         Stefan
>> 
>
> I tried to shift the `cif` related bits to `cconc--convert-function`,
> but my understanding of cconv.el isn't that great, so I wasn't
> successful at doing that :( Should I add a TODO to the change for the
> future?

Yes, please,


        Stefan