On Fri, Jan 25, 2019 at 6:22 PM Marek Polacek <pola...@redhat.com> wrote:
>
> On Fri, Jan 25, 2019 at 12:14:07PM -0500, Jason Merrill wrote:
> > On 1/25/19 12:09 PM, Marek Polacek wrote:
> > > On Fri, Jan 25, 2019 at 10:55:55AM -0600, Tim Song wrote:
> > > > On Thu, Jan 24, 2019 at 4:14 PM Jason Merrill <ja...@redhat.com> wrote:
> > > > >
> > > > > On 1/24/19 2:16 PM, Marek Polacek wrote:
> > > > > > This test ICEs since r159006 which added
> > > > > >
> > > > > >      type = ENUM_UNDERLYING_TYPE (type);
> > > > > >
> > > > > > to type_promotes_to.  In this test ENUM_UNDERLYING_TYPE is null 
> > > > > > because we
> > > > > > haven't yet parsed '}' of the enum and the underlying type isn't 
> > > > > > fixed, and
> > > > > > so checking TYPE_UNSIGNED crashed.
> > > > > >
> > > > > > I've added some checks to the test to see if the types seem to be 
> > > > > > OK; clang++
> > > > > > agrees.
> > > > > >
> > > > > > Bootstrapped/regtested on x86_64-linux, ok for trunk/8/7?
> > > > > >
> > > > > > 2019-01-24  Marek Polacek  <pola...@redhat.com>
> > > > > >
> > > > > >        PR c++/89024 - ICE with incomplete enum type.
> > > > > >        * cvt.c (type_promotes_to): Check if prom is non-null.
> > > > >
> > > > > 9.6/6: An enumeration whose underlying type is not fixed is an
> > > > > incomplete type from its point of declaration to immediately after the
> > > > > closing } of its enum-specifier, at which point it becomes a complete 
> > > > > type.
> > > > >
> > > > > So the conversion is ill-formed.
> > > > >
> > > > > Jason
> > > >
> > > > But the conversion in the example (in
> > > > decltype(__test_aux<_To1>(declval<_From1>())))
> > > > is in a SFINAE context, so shouldn't it gracefully fall back to the
> > > > `(...)` overload?
> > >
> > > I think so, and clang++ and icc also compile the testcase fine (and we 
> > > used to
> > > too, before r159006).
> >
> > Absolutely, the conversion being ill-formed means substitution fails, and we
> > reject that candidate.  I meant that we shouldn't get as far as
> > type_promotes_to for an incomplete type.
>
> Makes sense.  So here's another attempt:
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2019-01-25  Marek Polacek  <pola...@redhat.com>
>
>         PR c++/89024 - ICE with incomplete enum type.
>         * call.c (standard_conversion): When converting an
>         ARITHMETIC_TYPE_P to an incomplete type, return NULL.

OK.

Jason

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