bug#11348: 24.0.95; TAB-completion in shell-command produces d:\/foo on MS-Windows

[Drew Adams]

> > (Btw, what's the purpose of using eval-when-compile here?)
> 
> To avoid calling `concat' at run-time (especially within the loop).
> In older Emacsen, `concat' was marked as pure so the 
> byte-compiler would evaluate it at compile-time, but someone
> complained that it's not strictly correct because he wanted that
> (concat <foo>) is not `eq' to (concat <foo>).  I actually think
> this change was a mistake and would rather mark `concat' as pure again.

That sounds like the kind of explanation that would help readers as a comment in
the code.  If someone as attentive as Eli has to ask this then it might not hurt
to inform readers generally.

(Ignore my suggestion if inappropriate - I'm not following the thread etc.)