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* [Bug c++/98824] New: [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus
@ 2021-01-25 16:18 dimitri.gorokhovik at free dot fr
2021-01-27 15:33 ` [Bug c++/98824] " dimitri.gorokhovik at free dot fr
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: dimitri.gorokhovik at free dot fr @ 2021-01-25 16:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98824
Bug ID: 98824
Summary: [C++-20] function template non-type-class-arg
deduction fails with a reason that looks bogus
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dimitri.gorokhovik at free dot fr
Target Milestone: ---
The code:
template <auto> struct a {};
template <int i, a <i> v> constexpr auto f (a <v>) { return true; };
constexpr a <1> b;
auto const p = f (a <b> {});
when compiled with 'g++ -std=c++20 -c bug-14.cpp' (g++ (GCC) 11.0.0 20210123
(experimental)), produces:
bug-14.cpp:5:27: error: no matching function for call to ‘f(a<a<1>()>)’
5 | auto const p = f (a <b> {});
| ^
bug-14.cpp:2:42: note: candidate: ‘template<int i, a<i> v> constexpr auto
f(a<((const a<i>)v)>)’
2 | template <int i, a <i> v> constexpr auto f (a <v>) { return true; };
| ^
bug-14.cpp:2:42: note: template argument deduction/substitution failed:
bug-14.cpp:5:27: note: types ‘a<i>’ and ‘const a<1>’ have incompatible
cv-qualifiers
5 | auto const p = f (a <b> {});
clang-12 seems to accept it (hits a non-implemented feature in a subsequent
pass).
The diagnostics looks confusing/misleading:
-- compiler is aware of the constness of 'a <i>' -- see the signature of f() in
the note for line 2. And then it seemingly removes 'const' from 'const a <i>',
maybe expecting a certain strictness level in 'unify()'. However, unify() is
called with strict=UNIFY_ALLOW_NONE.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/98824] [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus
2021-01-25 16:18 [Bug c++/98824] New: [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus dimitri.gorokhovik at free dot fr
@ 2021-01-27 15:33 ` dimitri.gorokhovik at free dot fr
2021-08-17 9:24 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: dimitri.gorokhovik at free dot fr @ 2021-01-27 15:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98824
--- Comment #1 from Dimitri Gorokhovik <dimitri.gorokhovik at free dot fr> ---
It doesn't seem to contradict N4868 :-(
Modifying the code slightly (adding refs, splitting deduction across two fn
templates) didn't show any other differences from clang: all other modification
either both pass or both fail with the equivalent messages ("'i' cannot be
deduced"). This is the only one.
clang version:
Ubuntu clang version
12.0.0-++20201102052620+327bf5c2d91-1~exp1~20201102163303.210
Target: x86_64-pc-linux-gnu
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/98824] [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus
2021-01-25 16:18 [Bug c++/98824] New: [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus dimitri.gorokhovik at free dot fr
2021-01-27 15:33 ` [Bug c++/98824] " dimitri.gorokhovik at free dot fr
@ 2021-08-17 9:24 ` pinskia at gcc dot gnu.org
2022-01-18 5:50 ` bernie at codewiz dot org
2022-01-18 5:51 ` bernie at codewiz dot org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-08-17 9:24 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98824
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Keywords| |rejects-valid
Last reconfirmed| |2021-08-17
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/98824] [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus
2021-01-25 16:18 [Bug c++/98824] New: [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus dimitri.gorokhovik at free dot fr
2021-01-27 15:33 ` [Bug c++/98824] " dimitri.gorokhovik at free dot fr
2021-08-17 9:24 ` pinskia at gcc dot gnu.org
@ 2022-01-18 5:50 ` bernie at codewiz dot org
2022-01-18 5:51 ` bernie at codewiz dot org
3 siblings, 0 replies; 5+ messages in thread
From: bernie at codewiz dot org @ 2022-01-18 5:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98824
Bernie Innocenti <bernie at codewiz dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |bernie at codewiz dot org
--- Comment #3 from Bernie Innocenti <bernie at codewiz dot org> ---
Assuming this is the same bug, it's still present in g++ 12 as well as trunk:
https://godbolt.org/z/6r3bc3j15
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/98824] [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus
2021-01-25 16:18 [Bug c++/98824] New: [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus dimitri.gorokhovik at free dot fr
` (2 preceding siblings ...)
2022-01-18 5:50 ` bernie at codewiz dot org
@ 2022-01-18 5:51 ` bernie at codewiz dot org
3 siblings, 0 replies; 5+ messages in thread
From: bernie at codewiz dot org @ 2022-01-18 5:51 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98824
--- Comment #4 from Bernie Innocenti <bernie at codewiz dot org> ---
Are there any known workarounds?
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-01-18 5:51 UTC | newest]
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2021-01-25 16:18 [Bug c++/98824] New: [C++-20] function template non-type-class-arg deduction fails with a reason that looks bogus dimitri.gorokhovik at free dot fr
2021-01-27 15:33 ` [Bug c++/98824] " dimitri.gorokhovik at free dot fr
2021-08-17 9:24 ` pinskia at gcc dot gnu.org
2022-01-18 5:50 ` bernie at codewiz dot org
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