Stefan Kangas <stefankangas@gmail.com> writes:

> [...], all that is needed is to fix the formatting you describe in
> (1). That will give the desired behavior. [...] Regarding (2), I think
> compilation-mode already detects those as file locations, with no
> changes.  At least it does on current master.

As for (2), I recompiled Emacs from 'master' (498d31e9f05) to verify
your claim, but it does seem to hold.  I can reproduce the bug under
'emacs -Q' by following the reproduction steps.

However!  I did some thinking and realized two important facts:

(A) Even if the GNU standard supported tab-indented errors, as per (2),
it would not help, as Lua stack frames are not errors.

(B) People use older Lua versions, which will work forever, as they are
written in ANSI C, and so even if (1) is fixed upstream, we must support
the current error format as well.

After I realized that (A) and (B) are true, I used my morning to write a
patch that solves the problem properly.  I am attaching the patch to
this message.  Do you think the patch could be merged upstream?

Thank you for your time!

Rudy