[RFC] Fix for PR58201

[Paolo Carlini]

Hi Honza,

and thanks for the analysis, now I understand the issue a little more.

On 09/07/2013 10:28 AM, Jan Hubicka wrote:
> So it is just an accident that the line info is output sanely (if line 
> 9 is sane, I don't exactly know)
I would say that in general it's definitely sane, because that is the 
instantiation point. And 10 is wrong, too late, it points to the closing 
bracket.

However, I notice that clang doesn't even try to output a message having 
to do with line 9: if I understand correctly, if that operator cannot be 
mangled, that happens unconditionally, isn't something that may succeed. 
Thus I wonder if, instead of outputting garbage line numbers we could at 
least suppress in such cases the whole "In instantiation of..." part of 
the diagnostic, it would be better than garbage. Do we have a mechanism 
for that?

Now I also understand that this should be a very uncommon error message, 
but, I'm wondering, is it possible that other errors, for other issues, 
are also affected? That is, other diagnostic happening very late and 
sensitive to the recent rework?

Paolo.