[PATCH,c++] fix PR 45330, suggest alternatives for failed name lookups

[Nathan Froyd]

On Fri, Dec 03, 2010 at 11:22:45AM +0100, Dodji Seketeli wrote:
> Nathan Froyd <froydnj@codesourcery.com> writes:
> > @@ -449,7 +449,10 @@ unqualified_name_lookup_error (tree name)
> >    else
> >      {
> >        if (!objc_diagnose_private_ivar (name))
> > -        error ("%qD was not declared in this scope", name);
> > +	{
> > +	  error ("%qD was not declared in this scope", name);
> > +	  suggest_alternatives_for (name);
> > +	}
> 
> As we are gradually moving away from using the global input_location
> variable for better diagnostics maybe suggest_alternative could take a
> location parameter that ...
> 
> > +void
> > +suggest_alternatives_for (tree name)
> > +{
> 
> [...]
> 
> > +  if (n_searched >= max_to_search)
> > +    inform (input_location,
> > +	    "maximum limit of %d namespaces searched for %qE",
> > +	    max_to_search, name);
> 
> ... would be used here instead of using the global input_location.
> 
> OK, this really is a small nit. Sorry for the noise if it's
> irrelevant.

I think that's a good suggestion; I wasn't aware that we were trying to
move away from input_location.

One thing that really threw me from the diagnostics is that the C++
language-specifier formatter can set the location of the message
(error.c:cp_printer).  That seems a little weird--it would be better if
the location were explicit at the point of the diagnostic, rather than
arising from the things being printed.

I can do this pretty easily, but I think it will require unstatic'ing
location_of from error.c as my patch for PR 45329 does.  It doesn't
matter to me which goes in first; I suppose I can add the location_of
bits to whichever one does.

-Nathan