Re: Adding refactoring capabilities to Emacs

[Stefan Monnier <monnier@iro.umontreal.ca>]

> Though when I used that for a stepper I run into some ambiguities
> with atoms after macro expansion (described in section 4.1).  Might
> not be a problem here, as that problem was related to knowing
> which manifestations a given atom is actually evaluated.  And I'd
> say that's not a problem for the "rename" refactoring action.

The symbols-with-position approach avoids this problem (for symbols,
tho not for other data without identity list fixnums) because every
occurrence of a symbol returns a different "symbol with position" (and
then we need a hack to allow those different symbol-with-positions to
be `eq` nevertheless because that's what is needed at too many places
we can't control).

>> It's what's used in the byte-compiler to provide position info in
>> the warnings.
>
> Hmmm, and we know it doesn't always get things right... :-/ Namely
> it fails when there is more than one manifestation of the warning.
> But then again, maybe that's a problem of compilation, not
> reading, source-tracking or macro-expansion.

[ I can already hear Alan prepare his reply :-)  ]
Seriously, tho, the position is pretty damn exactly right almost every
time nowadays.  When it's not, it's not because the
"symbol-with-position" info is wrong but because it's missing, or
something else like that.


        Stefan