On 2025-12-04 21:14, Patrick Palka wrote:
> On Tue, 2 Dec 2025, Jason Merrill wrote:
>
> > On 12/2/25 3:37 AM, Egas Ribeiro wrote:
> > > On 2025-12-01 15:34, Patrick Palka wrote:
> > > > Hi Egas, thanks for tackling this bug!
> > > >
> > > > On Sun, 30 Nov 2025, Egas Ribeiro wrote:
> > > >
> > > > > Regtested on x86_64-pc-linux-gnu, OK for trunk?
> > > > >
> > > > > -- >8 --
> > > > >
> > > > > When checking a deleted explicit specialization in a SFINAE context,
> > > > > we were failing to propagate the error from mark_used. The call to
> > > > > resolve_nondeduced_context in convert_to_void correctly returned
> > > > > error_mark_node,
> > > >
> > > > I wonder actually whether resolve_nondeduced_context is correct to
> > > > return error_mark_node in this case. Sure the single X::g<0>
> > > > overload selected by resolve_nondeduced_context is deleted, but
> > > > should that imply an ODR-use of the overload? Maybe it should be the
> > > > responsibility of the caller to call mark_used, and we should remove the
> > > > mark_used in resolve_nondeduced_context.
> > > >
> > > > Note that resolve_nondeduced_context does not call mark_used when
> > > > the overload set is _not_ a template-id. So the caller will likely
> > > > have to call mark_used anyway to uniformly handle template-id and
> > > > non-template-id overloads.
> > > >
> > > > Jason, what do you think?
> > > >
> > > > > + if (expr == error_mark_node)
> > > > > + return false;
> > > >
> > > > If the above approach doesn't sound right then I agree that
> > > > mark_single_function as well as mark_used should return false
> > > > for error_mark_node.
> > >
> > > I looked into the usage for this case and I agree with Patrick. The
> > > comment on resolve_nondeduced_context cites DR 115 which is just about
> > > resolving a template-id to its specialization, nothing about ODR-use.
> > > So the mark_used call there seems out of place. That said, I think
> > > mark_single_function should still check for error_mark_node anyway,
> > > unless i understood something wrong about its usage.
> >
> > Currently mark_used doesn't return false for error_mark_node, and
> > mark_single_function should be consistent with mark_used. I'm open to
> > trying
> > returing false from both, but not just one.
> >
> > I also agree that the mark_used in resolve_nondeduced_context seems out of
> > place, and the caller should handle the marking, whether with a call to
> > mark_single_function or otherwise. Does removing the mark_used break
> > anything?
>
> That seems sufficient to fix the PR as well. Egas, wanna submit a patch
> taking that approach?
>
Yes, I will try submitting a patch either today or over the weekend for
this.
> >
> > > Happy to do whichever approach you prefer.
> > >
> >
> >
>
