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* [Bug c++/106734] New: [requires] std::same_as in compound requirements doesn't produce expected result
@ 2022-08-24 13:26 jakob at schmutz dot co.uk
2022-08-24 13:28 ` [Bug c++/106734] " jakob at schmutz dot co.uk
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: jakob at schmutz dot co.uk @ 2022-08-24 13:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106734
Bug ID: 106734
Summary: [requires] std::same_as in compound requirements
doesn't produce expected result
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jakob at schmutz dot co.uk
Target Milestone: ---
On gcc version 12.2.0 (and 11.3.0) I would expect the following code
```
#include <iostream>
struct Bar {
};
int main()
{
Bar bar;
constexpr bool same = requires
{
{ bar } -> std::same_as<Bar>;
};
constexpr bool conv = requires
{
{ bar } -> std::convertible_to<Bar>;
};
if constexpr (std::same_as<decltype(bar), Bar>)
{
std::cout << "AS SAME" << std::endl;
}
if constexpr (std::is_same_v<decltype(bar), Bar>)
{
std::cout << "IS SAME" << std::endl;
}
if constexpr (same)
{
std::cout << "REQUIRES SAME" << std::endl;
}
if constexpr (conv)
{
std::cout << "CONVERTIBLE" << std::endl;
}
return 0;
}
```
to return
```
AS SAME
IS SAME
REQUIRES SAME
CONVERTIBLE
```
based on how how [compound
requires](https://en.cppreference.com/w/cpp/language/requires) section reads
but instead it returns
```
IS SAME
REQUIRES SAME
CONVERTIBLE
```
compiled with `g++ temp.cpp -std=c++20`
compiling with `clang++ temp.cpp -std=c++20` produces the expected output
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/106734] [requires] std::same_as in compound requirements doesn't produce expected result
2022-08-24 13:26 [Bug c++/106734] New: [requires] std::same_as in compound requirements doesn't produce expected result jakob at schmutz dot co.uk
@ 2022-08-24 13:28 ` jakob at schmutz dot co.uk
2022-08-24 13:36 ` jakob at schmutz dot co.uk
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: jakob at schmutz dot co.uk @ 2022-08-24 13:28 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106734
--- Comment #1 from jakob at schmutz dot co.uk ---
> but instead it returns
>
> ```
> IS SAME
> REQUIRES SAME
> CONVERTIBLE
> ```
whoops this was supposed to be
```
AS SAME
IS SAME
CONVERTIBLE
```
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/106734] [requires] std::same_as in compound requirements doesn't produce expected result
2022-08-24 13:26 [Bug c++/106734] New: [requires] std::same_as in compound requirements doesn't produce expected result jakob at schmutz dot co.uk
2022-08-24 13:28 ` [Bug c++/106734] " jakob at schmutz dot co.uk
@ 2022-08-24 13:36 ` jakob at schmutz dot co.uk
2022-08-24 14:00 ` redi at gcc dot gnu.org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: jakob at schmutz dot co.uk @ 2022-08-24 13:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106734
--- Comment #2 from jakob at schmutz dot co.uk ---
Created attachment 53503
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53503&action=edit
preprocessed file
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/106734] [requires] std::same_as in compound requirements doesn't produce expected result
2022-08-24 13:26 [Bug c++/106734] New: [requires] std::same_as in compound requirements doesn't produce expected result jakob at schmutz dot co.uk
2022-08-24 13:28 ` [Bug c++/106734] " jakob at schmutz dot co.uk
2022-08-24 13:36 ` jakob at schmutz dot co.uk
@ 2022-08-24 14:00 ` redi at gcc dot gnu.org
2022-08-24 14:17 ` jakob at schmutz dot co.uk
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2022-08-24 14:00 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106734
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to jakob from comment #0)
> Bar bar;
> constexpr bool same = requires
> {
> { bar } -> std::same_as<Bar>;
This is false. The type of decltype((bar)) is Bar&.
So I think GCC is correct.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/106734] [requires] std::same_as in compound requirements doesn't produce expected result
2022-08-24 13:26 [Bug c++/106734] New: [requires] std::same_as in compound requirements doesn't produce expected result jakob at schmutz dot co.uk
` (2 preceding siblings ...)
2022-08-24 14:00 ` redi at gcc dot gnu.org
@ 2022-08-24 14:17 ` jakob at schmutz dot co.uk
2022-08-24 14:21 ` jakob at schmutz dot co.uk
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: jakob at schmutz dot co.uk @ 2022-08-24 14:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106734
--- Comment #4 from jakob at schmutz dot co.uk ---
(In reply to Jonathan Wakely from comment #3)
> (In reply to jakob from comment #0)
> > Bar bar;
> > constexpr bool same = requires
> > {
> > { bar } -> std::same_as<Bar>;
>
> This is false. The type of decltype((bar)) is Bar&.
>
> So I think GCC is correct.
Right but then why is `std::same_as<decltype(bar), Bar>` true? Shouldn't that
also be false then?
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/106734] [requires] std::same_as in compound requirements doesn't produce expected result
2022-08-24 13:26 [Bug c++/106734] New: [requires] std::same_as in compound requirements doesn't produce expected result jakob at schmutz dot co.uk
` (3 preceding siblings ...)
2022-08-24 14:17 ` jakob at schmutz dot co.uk
@ 2022-08-24 14:21 ` jakob at schmutz dot co.uk
2022-08-24 14:25 ` jakob at schmutz dot co.uk
2022-08-24 14:27 ` redi at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: jakob at schmutz dot co.uk @ 2022-08-24 14:21 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106734
--- Comment #5 from jakob at schmutz dot co.uk ---
oh I see `std::same_as<decltype((bar)), Bar>` is false
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/106734] [requires] std::same_as in compound requirements doesn't produce expected result
2022-08-24 13:26 [Bug c++/106734] New: [requires] std::same_as in compound requirements doesn't produce expected result jakob at schmutz dot co.uk
` (4 preceding siblings ...)
2022-08-24 14:21 ` jakob at schmutz dot co.uk
@ 2022-08-24 14:25 ` jakob at schmutz dot co.uk
2022-08-24 14:27 ` redi at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: jakob at schmutz dot co.uk @ 2022-08-24 14:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106734
jakob at schmutz dot co.uk changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #6 from jakob at schmutz dot co.uk ---
Will close then as I agree that GCC is correct
(I just found it a little confusing)
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/106734] [requires] std::same_as in compound requirements doesn't produce expected result
2022-08-24 13:26 [Bug c++/106734] New: [requires] std::same_as in compound requirements doesn't produce expected result jakob at schmutz dot co.uk
` (5 preceding siblings ...)
2022-08-24 14:25 ` jakob at schmutz dot co.uk
@ 2022-08-24 14:27 ` redi at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: redi at gcc dot gnu.org @ 2022-08-24 14:27 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106734
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
decltype(bar) and decltype((bar)) are not the same type.
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-08-24 14:27 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
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2022-08-24 13:26 [Bug c++/106734] New: [requires] std::same_as in compound requirements doesn't produce expected result jakob at schmutz dot co.uk
2022-08-24 13:28 ` [Bug c++/106734] " jakob at schmutz dot co.uk
2022-08-24 13:36 ` jakob at schmutz dot co.uk
2022-08-24 14:00 ` redi at gcc dot gnu.org
2022-08-24 14:17 ` jakob at schmutz dot co.uk
2022-08-24 14:21 ` jakob at schmutz dot co.uk
2022-08-24 14:25 ` jakob at schmutz dot co.uk
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