On 10/6/21 05:06, Jakub Jelinek wrote:
> On Tue, Oct 05, 2021 at 10:40:45PM -0400, Jason Merrill wrote:
>> I've switched to handling bases via binfo as discussed on IRC and added
>> spaceship-synth14.C to test proper base handling with virtual <=>. Here's
>> what I'm committing:
> 
> Thanks a lot.
> 
> I see spaceship-synth8.C is accepted without errors (| LOOKUP_NONVIRTUAL |
> LOOKUP_DEFAULTED didn't help it for me back when playing with it), but if I add
> 
> E e1, e2;
> auto x = e1 <=> e2;
> at the end of it, it is rejected:
> spaceship-synth8.C:26:17: error: use of deleted function ‘virtual constexpr std::strong_ordering E::operator<=>(const E&) const’
>     26 | auto x = e1 <=> e2;
>        |                 ^~
> spaceship-synth8.C:22:24: note: ‘virtual constexpr std::strong_ordering E::operator<=>(const E&) const’ is implicitly deleted because the default definition would be ill-formed:
>     22 |   std::strong_ordering operator<=>(const E&) const override = default;
>        |                        ^~~~~~~~
> spaceship-synth8.C:21:8: error: no match for ‘operator<=>’ (operand types are ‘const D’ and ‘const D’)
>     21 | struct E : D {
>        |        ^
> spaceship-synth8.C:19:32: note: candidate: ‘virtual std::strong_ordering D::operator<=>(const E&) const’ (reversed)
>     19 |   virtual std::strong_ordering operator<=>(const struct E&) const = 0;
>        |                                ^~~~~~~~
> spaceship-synth8.C:19:44: note:   no known conversion for argument 1 from ‘const D’ to ‘const E&’
>     19 |   virtual std::strong_ordering operator<=>(const struct E&) const = 0;
>        |                                            ^~~~~~~~~~~~~~~
> 
> Is that ok (i.e. whether it is accepted or rejected when the operator<=>
> is actually not called falls into "no diagnostics required" category)?

It's not even NDR, it's implicitly deleted, so it's well-formed until 
called.

> Note, before this fix we were accepting it even with those
> E e1, e2;
> auto x = e1 <=> e2;
> lines in there.  Perhaps we want to copy spaceship-synth8.C to another
> test that will add those two lines and check for the errors...

Done: