bug#67455: Record source position, etc., in doc strings, and use this in *Help* and backtraces.

[Alan Mackenzie <acm@muc.de>]

Hello, Stefan.

On Mon, Dec 04, 2023 at 13:33:25 -0500, Stefan Monnier wrote:
> > I've committed the first stage of this implementation in the new git
> > branch feature/positioned-lambdas.

> Haven't had enough time to look closely, so just some quick early comment.

.....

I'm making steady, if not rapid, progress on the use of doc strings to
store position information.  There have been several unexpected
problems (which is only to be expected), all of which, bar one, I've
been able to solve.

The problem that has thrown me is the use of the doc string in oclosures
for other purposes.  For example, in position 2 of a lambda form,
appears something like

    (:documentation 'oclosure-accessor)

..  My current code is expecting, on encountering (:documentation ...),
for the cadr to be a string, onto which it can add a concat form which
will prefix the position information.

A solution to this problem would be to move the above symbol to element
2 of the list, something like

    (:documentation nil 'oclosure-accessor)

, so that my new code could place its information in the now vacant
position 1, giving something like

    (:documentation ";POS\36\0\0\0 [ .... ]\n" 'oclosure-accessor)

..  What do you think of this idea, and have you any better ideas for a
solution to the problem?

>         Stefan

-- 
Alan Mackenzie (Nuremberg, Germany).