Re: [C++ PATCH] Refactor implicit function template implementation and fix 58534, 58536, 58548, 58549 and 58637.

[Adam Butcher <adam at jessamine dot co dot uk>]

On 2013-11-10 6:10, Jason Merrill wrote:
> Hmm, actually I think messing with the non-pack's decl is dangerous,
> and we should come up with a new decl for the pack instead.  I think
> you can use reduce_template_parm_level with a "levels" argument of 0
> to build a new decl and parm index.
I actually did this in one of my experiments and it worked fine.
Although I also had to update the template parm list with new decl:

  TREE_VALUE (TREE_VEC_ELT (current, i)) = TREE_CHAIN (t);

At that point I had the convert function in pt.c an operating directly
on current_template_parms (also having direct access to the two statics
required; reduce_template_parm_level and canonical_type_parameter).

I can't think of a case where we'd want to make this substitution in
anything but the current_template_parms so maybe moving the convert
function back into to pt.c and removing the 'current' parm from it
might be best?

> And if we're doing that, setting TYPE_STUB_DECL and TYPE_NAME is
> indeed necessary.
>
> > Only for the sake of not exposing this (currently static) function 
> > from
> > pt.c (or moving the pack convert function into pt.c).  My original 
> > impl
> > did extern canonical_type_parameter and use that and I think it 
> > worked
> > as expected.  Would that be preferred?
>
> Yes.  Please declare it in cp-tree.h rather than within the function.
Will do.  Unless, as suggested above, we go for moving
convert_generic_types_to_packs into pt.c in which case exposing these
internals won't be necessary.

Cheers,
Adam