bug#40671: [DOC] modify literal objects

[Paul Eggert]

On 4/19/20 9:59 AM, Mattias Engdegård wrote:
> What about we add a separate section about literals of all types, why they 
> should be treated as immutable even though mutation currently isn't detected or 
> disallowed at runtime, and recommended ways of coping with it (constructor 
> functions, copy-sequence)? It would serve as a point of reference for all 
> sections describing destructive operations.

In my recent patches to the emacs-27 branch I added a section "Constants and 
Mutability" that discusses many of these issues. It's a fundamental topic so I 
put the new section into doc/lispref/objects.texi, and cross-referenced it from 
the destructive-operation sections.

I didn't think of recommending ways of coping with it, and that's a good 
suggestion. I'm not sure that the coping-mechanism discussion belongs in 
objects.texi, though, as it's pragmatic rather than fundamental.

>  There is also a need for some cautionary text in the backquote section.

Yes, my recent patches added a brief note there.

> I'd volunteer to write it all but won't do the work just to have it shot down 
> on general principles.

I know the feeling.