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* [Bug c++/107417] New: g++ fails to recognize parameter pack in requires-expression
@ 2022-10-26 15:25 jwjagersma at gmail dot com
2022-10-26 16:32 ` [Bug c++/107417] " redi at gcc dot gnu.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: jwjagersma at gmail dot com @ 2022-10-26 15:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107417
Bug ID: 107417
Summary: g++ fails to recognize parameter pack in
requires-expression
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:
$ cat fold.cpp
template<typename... T>
requires (requires (T x) { x; } and ...)
auto func(T...) { }
g++ seems to forget that T is a parameter pack:
$ g++ -std=c++20 fold.cpp
fold.cpp:2:11: error: operand of fold expression has no unexpanded parameter
packs
2 | requires (requires (T x) { x; } and ...)
| ^~~~~~~~~~~~~~~~~~~~~
This issue is present on both 12.2 and latest 13.0. Clang and msvc do accept
it.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/107417] g++ fails to recognize parameter pack in requires-expression
2022-10-26 15:25 [Bug c++/107417] New: g++ fails to recognize parameter pack in requires-expression jwjagersma at gmail dot com
@ 2022-10-26 16:32 ` redi at gcc dot gnu.org
2022-10-26 19:06 ` ppalka at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: redi at gcc dot gnu.org @ 2022-10-26 16:32 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107417
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Keywords| |accepts-invalid,
| |rejects-valid
Ever confirmed|0 |1
Last reconfirmed| |2022-10-26
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I think the underlying issue is that it accepts the pack without expansion:
template<typename... T>
requires (requires (T x) { x; })
auto func(T...) { }
And so the error about "no unexpanded parameter packs" is correct, the AST
doesn't contain any. But it should do, the requires-expression is a pack
expression that must be expanded (e.g. in a fold expression).
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/107417] g++ fails to recognize parameter pack in requires-expression
2022-10-26 15:25 [Bug c++/107417] New: g++ fails to recognize parameter pack in requires-expression jwjagersma at gmail dot com
2022-10-26 16:32 ` [Bug c++/107417] " redi at gcc dot gnu.org
@ 2022-10-26 19:06 ` ppalka at gcc dot gnu.org
2022-12-04 15:47 ` cvs-commit at gcc dot gnu.org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: ppalka at gcc dot gnu.org @ 2022-10-26 19:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107417
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |ppalka at gcc dot gnu.org
CC| |ppalka at gcc dot gnu.org
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/107417] g++ fails to recognize parameter pack in requires-expression
2022-10-26 15:25 [Bug c++/107417] New: g++ fails to recognize parameter pack in requires-expression jwjagersma at gmail dot com
2022-10-26 16:32 ` [Bug c++/107417] " redi at gcc dot gnu.org
2022-10-26 19:06 ` ppalka at gcc dot gnu.org
@ 2022-12-04 15:47 ` cvs-commit at gcc dot gnu.org
2022-12-04 15:47 ` ppalka at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-12-04 15:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107417
--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:079add3ad39d6620d34665dd9c26c21951eb657c
commit r13-4483-g079add3ad39d6620d34665dd9c26c21951eb657c
Author: Patrick Palka <ppalka@redhat.com>
Date: Sun Dec 4 10:47:24 2022 -0500
c++: pack in requires-expr parm list [PR107417]
Here find_parameter_packs_r isn't detecting the pack T inside the
requires-expr's parameter list ultimately because cp_walk_trees
deliberately avoids walking the list so as to avoid false positives in
the unexpanded pack checker.
But it should still be fine to walk the TREE_TYPE of each parameter,
which we already need to do from for_each_template_parm_r, and is
sufficient to fix the testcase.
PR c++/107417
gcc/cp/ChangeLog:
* pt.cc (for_each_template_parm_r) <case REQUIRES_EXPR>: Move
walking of the TREE_TYPE of each parameter to ...
* tree.cc (cp_walk_subtrees) <case REQUIRES_EXPR>: ... here.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-requires33.C: New test.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/107417] g++ fails to recognize parameter pack in requires-expression
2022-10-26 15:25 [Bug c++/107417] New: g++ fails to recognize parameter pack in requires-expression jwjagersma at gmail dot com
` (2 preceding siblings ...)
2022-12-04 15:47 ` cvs-commit at gcc dot gnu.org
@ 2022-12-04 15:47 ` ppalka at gcc dot gnu.org
2022-12-19 16:54 ` cvs-commit at gcc dot gnu.org
2022-12-19 16:56 ` ppalka at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: ppalka at gcc dot gnu.org @ 2022-12-04 15:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107417
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |12.3
--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed on trunk so far.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/107417] g++ fails to recognize parameter pack in requires-expression
2022-10-26 15:25 [Bug c++/107417] New: g++ fails to recognize parameter pack in requires-expression jwjagersma at gmail dot com
` (3 preceding siblings ...)
2022-12-04 15:47 ` ppalka at gcc dot gnu.org
@ 2022-12-19 16:54 ` cvs-commit at gcc dot gnu.org
2022-12-19 16:56 ` ppalka at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-12-19 16:54 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107417
--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:b428bb449be1bdbbd4000b51bb7c665981dc8c8f
commit r12-8996-gb428bb449be1bdbbd4000b51bb7c665981dc8c8f
Author: Patrick Palka <ppalka@redhat.com>
Date: Sun Dec 4 10:47:24 2022 -0500
c++: pack in requires-expr parm list [PR107417]
Here find_parameter_packs_r isn't detecting the pack T inside the
requires-expr's parameter list ultimately because cp_walk_trees
deliberately avoids walking the list so as to avoid false positives in
the unexpanded pack checker.
But it should still be fine to walk the TREE_TYPE of each parameter,
which we already need to do from for_each_template_parm_r, and is
sufficient to fix the testcase.
PR c++/107417
gcc/cp/ChangeLog:
* pt.cc (for_each_template_parm_r) <case REQUIRES_EXPR>: Move
walking of the TREE_TYPE of each parameter to ...
* tree.cc (cp_walk_subtrees) <case REQUIRES_EXPR>: ... here.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-requires33.C: New test.
(cherry picked from commit 079add3ad39d6620d34665dd9c26c21951eb657c)
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/107417] g++ fails to recognize parameter pack in requires-expression
2022-10-26 15:25 [Bug c++/107417] New: g++ fails to recognize parameter pack in requires-expression jwjagersma at gmail dot com
` (4 preceding siblings ...)
2022-12-19 16:54 ` cvs-commit at gcc dot gnu.org
@ 2022-12-19 16:56 ` ppalka at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: ppalka at gcc dot gnu.org @ 2022-12-19 16:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107417
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|ASSIGNED |RESOLVED
--- Comment #5 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed for GCC 12.3/13, thanks for the bug report.
^ permalink raw reply [flat|nested] 7+ messages in thread
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2022-10-26 15:25 [Bug c++/107417] New: g++ fails to recognize parameter pack in requires-expression jwjagersma at gmail dot com
2022-10-26 16:32 ` [Bug c++/107417] " redi at gcc dot gnu.org
2022-10-26 19:06 ` ppalka at gcc dot gnu.org
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