On Wed, 4 Sep 2024, Marek Polacek wrote:
> On Wed, Sep 04, 2024 at 10:58:25AM -0400, Jason Merrill wrote:
> > On 9/3/24 6:12 PM, Marek Polacek wrote:
> > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/14?
> >
> > The change to return bool seems like unrelated cleanup; please push that
> > separately on trunk only.
>
> Done.
>
> > > + /* We can also have:
> > > +
> > > + template <template <typename T, typename T::type TT> typename X>
> > > + void func() {}
> > > + template <typename U, int I>
> > > + struct Y {};
> > > + void g() { func<Y>(); }
> > > +
> > > + where we are not in a template, but the type of PARM is T::type
> > > + and dependent_type_p doesn't want to see a TEMPLATE_TYPE_PARM
> > > + outside a template. */
> > > + ++processing_template_decl;
> > > tree t = tsubst (TREE_TYPE (parm), outer_args, complain,
> > > in_decl);
> > > + --processing_template_decl;
> > > if (!uses_template_parms (t)
> > > && !same_type_p (t, TREE_TYPE (arg)))
> >
> > This looks like the pattern Patrick just removed from type_unification_real
> > for PR101463. Do we want to make the same change here?
The pattern does seem similar, but I can't see the benefit of making the
same change here. In type_unification_real the change made dependent vs
non-dependent deduction more uniform by removing the dependence tests.
But nothing can be made more uniform here AFAICT. At best we can use
find_template_parameters to see if 'parm' depends on outer template
parameters and avoid the substitution if so. But both uses_template_parms
tests need to remain, I think. Even if 'parm' doesn't depend on outer
template parameters, it seems we still want to succeed if it's overall
dependent as in the testcase from the PR. Likewise if 'arg' is overall
dependent and 'parm' isn't.
>
> Interesting. Sorry, this may be silly, but I'm not sure I can do that
> here: find_template_parameters wants "the template parameters in scope"
> but I don't think I have that here.
You could probably pass the DECL_TEMPLATE_PARMS of parm_tmpl or arg_tmpl
of its caller.
