[C++] deprecate overload resolution extension?

[Jason Merrill]

>>>>> "dewar" == dewar  <dewar@gnat.com> writes:

>> However, I think we need some kind of unanimous consent before we
>> proceed.  Another compromise would be to keep the code (which unlike
>> some other extensions is simple, compartmentalized, well-documented,
>> and safe), keep the !pedantic condition, but add a pedwarn.  That way
>> pedantic users just get errors (instead of this rule kicking in, which
>> they likely won't understand) and non-pedantic users get a warning.

> I think it's a bad idea not to flag this as an error. I am all in favor
> of well conceived extensions that are permitted in non-pedantic mode,
> but I just don't see this particular extension as well conceived, it
> seems like a mistake to me, why perpetuate a mistake? The proper user
> action is to disambiguate anyway, and I see no real downside in forcing
> this desirable disambiguation.

We will be forcing the disambiguation; in the C++ frontend, pedwarns are
errors by default.  But I would like people to be able to build code that
relies on this with -fpermissive; again, I put this extension in because
things were breaking without it (though I don't remember what).

Jason