[Bug c++/109181] requires expression type requirement rejects valid type when it is a nested member template
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109181 Patrick Palka changed: What|Removed |Added Status|NEW |RESOLVED Resolution|--- |DUPLICATE --- Comment #7 from Patrick Palka --- (In reply to waffl3x from comment #6) > PR 110927 presents a similar use case that originally lead me to this bug, I > also posted the workarounds that I had since discovered there. If anyone > coming across this bug is looking for a solution you can find them there. Interesting, thanks! I'm going to call this PR a dup of the newer one then, since that one has your workarounds. *** This bug has been marked as a duplicate of bug 110927 ***
[Bug c++/109181] requires expression type requirement rejects valid type when it is a nested member template
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109181 --- Comment #6 from waffl3x --- PR 110927 presents a similar use case that originally lead me to this bug, I also posted the workarounds that I had since discovered there. If anyone coming across this bug is looking for a solution you can find them there.
[Bug c++/109181] requires expression type requirement rejects valid type when it is a nested member template
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109181
--- Comment #5 from waffl3x ---
(In reply to Patrick Palka from comment #3)
> A workaround is to just remove the unneeded 'template' after the :: in this
> case. Or is there an example where the template keyword is needed that we
> incorrectly reject?
In my original use case, A in `inline constexpr bool go = requires{typename
A::template B;};` would have been dependent, I included the template
keyword because of that but it should have occurred to me that the example I
presented doesn't need it, I'm not sure what the standard requires for this
sort of thing though.
When I reduce I just remove everything that isn't required to get the result
I'm looking for, I should have realized that changing the semantics of the
example might create confusion and in the future I think I will also include a
reduced version that comes closer to the problem I actually encountered, I
imagine that it will be helpful even if it's not actually the most reduced
version.
I'll try to create an example that reflects my use case better as soon as I
can.
[Bug c++/109181] requires expression type requirement rejects valid type when it is a nested member template
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109181
--- Comment #4 from Andrew Pinski ---
(In reply to Patrick Palka from comment #3)
> A workaround is to just remove the unneeded 'template' after the :: in this
> case. Or is there an example where the template keyword is needed that we
> incorrectly reject?
I could not find an example.
I did find an example where the template is removed clang rejects it but gcc
does not:
struct A {
template
using B = int;
};
template
T C();
template
bool go = requires{typename decltype(C())::template B;};
bool a = go;
[Bug c++/109181] requires expression type requirement rejects valid type when it is a nested member template
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109181 Patrick Palka changed: What|Removed |Added CC||ppalka at gcc dot gnu.org --- Comment #3 from Patrick Palka --- A workaround is to just remove the unneeded 'template' after the :: in this case. Or is there an example where the template keyword is needed that we incorrectly reject?
[Bug c++/109181] requires expression type requirement rejects valid type when it is a nested member template
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109181
--- Comment #2 from waffl3x ---
(In reply to Andrew Pinski from comment #1)
> Confirmed.
> Goes away the way back when -fconcepts support was originally added in GCC
> 6. You can see that with this testcase:
> ```
> struct A {
> template
> using B = int;
> };
>
> template
> bool go = requires{typename A::template B;};
> ```
>
> Note back in GCC 6, you needed `-std=c++17 -fconcepts` and also requires was
> only allowed for templates too ..
Ah damn, I'll try to keep in mind that I can use the old enabling flags to go
further back. I'm glad this one wasn't a duplicate, heres hoping I don't find
another bug today
[Bug c++/109181] requires expression type requirement rejects valid type when it is a nested member template
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109181
Andrew Pinski changed:
What|Removed |Added
Last reconfirmed||2023-03-18
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Known to fail||10.1.0, 12.1.0, 13.0,
||6.1.0, 7.1.0
--- Comment #1 from Andrew Pinski ---
Confirmed.
Goes away the way back when -fconcepts support was originally added in GCC 6.
You can see that with this testcase:
```
struct A {
template
using B = int;
};
template
bool go = requires{typename A::template B;};
```
Note back in GCC 6, you needed `-std=c++17 -fconcepts` and also requires was
only allowed for templates too ..
