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* [Bug c++/107429] New: misdiagnosed "constraint depends on itself" in overloaded functions
@ 2022-10-26 21:03 jwjagersma at gmail dot com
2022-10-27 12:42 ` [Bug c++/107429] " ppalka at gcc dot gnu.org
2022-10-27 16:16 ` jwjagersma at gmail dot com
0 siblings, 2 replies; 3+ messages in thread
From: jwjagersma at gmail dot com @ 2022-10-26 21:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107429
Bug ID: 107429
Summary: misdiagnosed "constraint depends on itself" in
overloaded functions
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jwjagersma at gmail dot com
Target Milestone: ---
Given the following code:
struct tag_foo { } inline constexpr foo;
struct tag_bar { } inline constexpr bar;
template<typename... T>
auto f(tag_foo, T... x)
{
return (x + ...);
}
template<typename... T>
concept fooable = requires (T... x) { f(foo, x...); };
template<typename... T> requires (fooable<T...>)
auto f(tag_bar, T... x)
{
return f(foo, x...);
}
auto test()
{
return f(bar, 1, 2, 3);
}
g++ claims that "satisfaction of atomic constraint [...] depends on itself",
but the overload of 'f()' that is checked by 'fooable' is not constrained in
any way.
I am not 100% sure if this is valid code, but clang and msvc do not make the
same complaint, so I'm inclined to believe g++ is in error here.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/107429] misdiagnosed "constraint depends on itself" in overloaded functions
2022-10-26 21:03 [Bug c++/107429] New: misdiagnosed "constraint depends on itself" in overloaded functions jwjagersma at gmail dot com
@ 2022-10-27 12:42 ` ppalka at gcc dot gnu.org
2022-10-27 16:16 ` jwjagersma at gmail dot com
1 sibling, 0 replies; 3+ messages in thread
From: ppalka at gcc dot gnu.org @ 2022-10-27 12:42 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107429
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
CC| |ppalka at gcc dot gnu.org
Resolution|--- |DUPLICATE
--- Comment #1 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Thanks for the bug report. This is a consequence of CWG2369, and the
constraint recursion diagnosis is strictly speaking correct correct. I think
other compilers accept it because they don't fully implement
https://wg21.link/cwg2369 which moved the constraint satisfaction check during
template argument deduction to _before_ the checking non-dependent conversions.
A workaround (that should be valid pre- and post-CWG2369) is to encode the
non-dependent conversion in the constrained overload of f as an additional
constraint that's checked before the fooable constraint:
template<std::convertible_to<tag_bar> U, typename... T> requires
(fooable<T...>)
auto f(U, T... x)
see PR99599 and its dups for more info
*** This bug has been marked as a duplicate of bug 99599 ***
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/107429] misdiagnosed "constraint depends on itself" in overloaded functions
2022-10-26 21:03 [Bug c++/107429] New: misdiagnosed "constraint depends on itself" in overloaded functions jwjagersma at gmail dot com
2022-10-27 12:42 ` [Bug c++/107429] " ppalka at gcc dot gnu.org
@ 2022-10-27 16:16 ` jwjagersma at gmail dot com
1 sibling, 0 replies; 3+ messages in thread
From: jwjagersma at gmail dot com @ 2022-10-27 16:16 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107429
--- Comment #2 from jwjagersma at gmail dot com ---
Thanks, I thought I searched but somehow missed that PR.
From a user perspective it seems very surprising that this workaround compiles,
but the obvious implementation doesn't. I do hope it gets addressed someday.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-10-27 16:16 UTC | newest]
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2022-10-26 21:03 [Bug c++/107429] New: misdiagnosed "constraint depends on itself" in overloaded functions jwjagersma at gmail dot com
2022-10-27 12:42 ` [Bug c++/107429] " ppalka at gcc dot gnu.org
2022-10-27 16:16 ` jwjagersma at gmail dot com
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