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* [Bug c++/102590] New: Templated operations on variables in structured binding don't work when templated functions/lambdas require type deduction
@ 2021-10-04 11:06 1997.rajatjain at gmail dot com
2021-10-04 11:14 ` [Bug c++/102590] " pinskia at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: 1997.rajatjain at gmail dot com @ 2021-10-04 11:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102590
Bug ID: 102590
Summary: Templated operations on variables in structured
binding don't work when templated functions/lambdas
require type deduction
Product: gcc
Version: 8.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: 1997.rajatjain at gmail dot com
Target Milestone: ---
Foreach loops written with a structured-binding declaration error out if any of
the captured types contains a template member-function which is used inside the
loop.
This only happens if such a loop is placed inside a templated lambda/function.
A minimal example of the above is:
struct Foo
{
template<typename T>
T get() const
{
return static_cast<T>(0);
}
};
template<typename T>
void error_func(T elem)
{
std::array<std::pair<int, Foo>, 1> arr;
for(const auto& [_, val] : arr)
{
val.get<int>(); // Error here
}
}
The error disappears if T is replaced with any concrete type. It also
disappears if instead of structured bindings, a tuple is used with auto type
specifier.
The above code also works if one writes:
const auto& [_, val] = arr[0];
val.get<int>();
Compilation flags: -std=c++17
Reported error:
test.cpp:19:17: error: expected primary-expression before 'int'
val.get<int>();
^~~
test.cpp:19:17: error: expected ';' before 'int'
val.get<int>();
^~~
;
^ permalink raw reply [flat|nested] 5+ messages in thread* [Bug c++/102590] Templated operations on variables in structured binding don't work when templated functions/lambdas require type deduction 2021-10-04 11:06 [Bug c++/102590] New: Templated operations on variables in structured binding don't work when templated functions/lambdas require type deduction 1997.rajatjain at gmail dot com @ 2021-10-04 11:14 ` pinskia at gcc dot gnu.org 2021-10-04 11:31 ` 1997.rajatjain at gmail dot com ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-10-04 11:14 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102590 --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- My bet is gcc mistaken it for being a dependent type which meaning you can use the template keyword to workaround the issue. Also gcc 8.x series is over 3 years old so this might be fixed already in a newer version of gcc. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/102590] Templated operations on variables in structured binding don't work when templated functions/lambdas require type deduction 2021-10-04 11:06 [Bug c++/102590] New: Templated operations on variables in structured binding don't work when templated functions/lambdas require type deduction 1997.rajatjain at gmail dot com 2021-10-04 11:14 ` [Bug c++/102590] " pinskia at gcc dot gnu.org @ 2021-10-04 11:31 ` 1997.rajatjain at gmail dot com 2021-10-05 5:41 ` [Bug c++/102590] structured binding inside for all loop thinks it is type depedent when it is not pinskia at gcc dot gnu.org 2021-10-05 5:43 ` [Bug c++/102590] structured binding inside for all loop thinks it is type depedent when it is not (inside a template) pinskia at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: 1997.rajatjain at gmail dot com @ 2021-10-04 11:31 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102590 --- Comment #2 from Rajat Jain <1997.rajatjain at gmail dot com> --- Yeah .template works as well. This is in the latest release too. I wasn't sure whether I should write the oldest version that this is in (since other 8.x releases would need a patch as well), or the latest. Let me change that. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/102590] structured binding inside for all loop thinks it is type depedent when it is not. 2021-10-04 11:06 [Bug c++/102590] New: Templated operations on variables in structured binding don't work when templated functions/lambdas require type deduction 1997.rajatjain at gmail dot com 2021-10-04 11:14 ` [Bug c++/102590] " pinskia at gcc dot gnu.org 2021-10-04 11:31 ` 1997.rajatjain at gmail dot com @ 2021-10-05 5:41 ` pinskia at gcc dot gnu.org 2021-10-05 5:43 ` [Bug c++/102590] structured binding inside for all loop thinks it is type depedent when it is not (inside a template) pinskia at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-10-05 5:41 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102590 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Keywords| |rejects-valid Summary|Templated operations on |structured binding inside |variables in structured |for all loop thinks it is |binding don't work when |type depedent when it is |templated functions/lambdas |not. |require type deduction | Ever confirmed|0 |1 Last reconfirmed| |2021-10-05 --- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Reduced testcase (without any includes): struct Foo { template<class T> T get() const { return 0; } }; struct f { int t; Foo t1; }; template<typename T> void error_func(T elem) { f arr[1]; for(const auto& [_, val] : arr) { val.get<int>(); // Error here } } ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/102590] structured binding inside for all loop thinks it is type depedent when it is not (inside a template) 2021-10-04 11:06 [Bug c++/102590] New: Templated operations on variables in structured binding don't work when templated functions/lambdas require type deduction 1997.rajatjain at gmail dot com ` (2 preceding siblings ...) 2021-10-05 5:41 ` [Bug c++/102590] structured binding inside for all loop thinks it is type depedent when it is not pinskia at gcc dot gnu.org @ 2021-10-05 5:43 ` pinskia at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-10-05 5:43 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102590 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |DUPLICATE Status|NEW |RESOLVED --- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Dup of bug 84469. *** This bug has been marked as a duplicate of bug 84469 *** ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-10-05 5:43 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-10-04 11:06 [Bug c++/102590] New: Templated operations on variables in structured binding don't work when templated functions/lambdas require type deduction 1997.rajatjain at gmail dot com 2021-10-04 11:14 ` [Bug c++/102590] " pinskia at gcc dot gnu.org 2021-10-04 11:31 ` 1997.rajatjain at gmail dot com 2021-10-05 5:41 ` [Bug c++/102590] structured binding inside for all loop thinks it is type depedent when it is not pinskia at gcc dot gnu.org 2021-10-05 5:43 ` [Bug c++/102590] structured binding inside for all loop thinks it is type depedent when it is not (inside a template) pinskia at gcc dot gnu.org
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