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* [Bug c++/98077] New: C++ 17: Using alias template bug in gcc @ 2020-12-01 7:15 juergen.reiss at gmx dot de 2020-12-01 10:33 ` [Bug c++/98077] " redi at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: juergen.reiss at gmx dot de @ 2020-12-01 7:15 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98077 Bug ID: 98077 Summary: C++ 17: Using alias template bug in gcc Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: juergen.reiss at gmx dot de Target Milestone: --- The error was reported here: https://stackoverflow.com/questions/65079471/c-17-using-alias-template-bug-in-gcc A demo is here: https://godbolt.org/z/avGv3n ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/98077] C++ 17: Using alias template bug in gcc 2020-12-01 7:15 [Bug c++/98077] New: C++ 17: Using alias template bug in gcc juergen.reiss at gmx dot de @ 2020-12-01 10:33 ` redi at gcc dot gnu.org 2020-12-01 13:11 ` redi at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2020-12-01 10:33 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98077 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |WAITING Last reconfirmed| |2020-12-01 Ever confirmed|0 |1 --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- Please see https://gcc.gnu.org/bugs for the requested info. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/98077] C++ 17: Using alias template bug in gcc 2020-12-01 7:15 [Bug c++/98077] New: C++ 17: Using alias template bug in gcc juergen.reiss at gmx dot de 2020-12-01 10:33 ` [Bug c++/98077] " redi at gcc dot gnu.org @ 2020-12-01 13:11 ` redi at gcc dot gnu.org 2020-12-01 13:15 ` redi at gcc dot gnu.org 2021-06-24 19:25 ` ppalka at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2020-12-01 13:11 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98077 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|WAITING |NEW Keywords| |rejects-valid --- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> --- The testcase from the godbolt link is: // { dg-options "-std=gnu++17" } #include <functional> template <typename T> struct CallableTrait; template <typename R, typename... Args> struct CallableTrait<std::function<R(Args...)>> { using ReturnType = R; }; template <typename Callable> using CallableTraitT = CallableTrait<decltype(std::function{std::declval<Callable>()})>; template <typename Callable> auto test(Callable&&) { using CallableInfo = CallableTraitT<Callable>; static_assert(!std::is_void_v<typename CallableInfo::ReturnType>); } int main() { test([]() { return 42; }); } It requires at least C++17. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/98077] C++ 17: Using alias template bug in gcc 2020-12-01 7:15 [Bug c++/98077] New: C++ 17: Using alias template bug in gcc juergen.reiss at gmx dot de 2020-12-01 10:33 ` [Bug c++/98077] " redi at gcc dot gnu.org 2020-12-01 13:11 ` redi at gcc dot gnu.org @ 2020-12-01 13:15 ` redi at gcc dot gnu.org 2021-06-24 19:25 ` ppalka at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2020-12-01 13:15 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98077 --- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Reduced: template<typename T> T&& declval(); template<typename R> struct function { template<typename T> function(T) { } }; template<typename T> function(T) -> function<decltype(declval<T>()())>; template<typename T> constexpr bool is_void_v = false; template<> constexpr bool is_void_v<void> = true; template <typename T> struct CallableTrait; template <typename R> struct CallableTrait<function<R>> { using ReturnType = R; }; template <typename Callable> using CallableTraitT = CallableTrait<decltype(function{declval<Callable>()})>; template <typename Callable> auto test(Callable&&) { using CallableInfo = CallableTraitT<Callable>; static_assert(!is_void_v<typename CallableInfo::ReturnType>); } int main() { test([]() { return 42; }); } 98077.C: In instantiation of ‘auto test(Callable&&) [with Callable = main()::<lambda()>]’: 98077.C:34:29: required from here 98077.C:29:20: error: invalid use of incomplete type ‘struct CallableTrait<main()::<lambda()> >’ 29 | static_assert(!is_void_v<typename CallableInfo::ReturnType>); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 98077.C:14:8: note: declaration of ‘struct CallableTrait<main()::<lambda()> >’ 14 | struct CallableTrait; | ^~~~~~~~~~~~~ ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/98077] C++ 17: Using alias template bug in gcc 2020-12-01 7:15 [Bug c++/98077] New: C++ 17: Using alias template bug in gcc juergen.reiss at gmx dot de ` (2 preceding siblings ...) 2020-12-01 13:15 ` redi at gcc dot gnu.org @ 2021-06-24 19:25 ` ppalka at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: ppalka at gcc dot gnu.org @ 2021-06-24 19:25 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98077 Patrick Palka <ppalka at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |ppalka at gcc dot gnu.org Status|NEW |RESOLVED Resolution|--- |DUPLICATE --- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> --- This is essentially a dup of the older 91911, I think *** This bug has been marked as a duplicate of bug 91911 *** ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-06-24 19:25 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-12-01 7:15 [Bug c++/98077] New: C++ 17: Using alias template bug in gcc juergen.reiss at gmx dot de 2020-12-01 10:33 ` [Bug c++/98077] " redi at gcc dot gnu.org 2020-12-01 13:11 ` redi at gcc dot gnu.org 2020-12-01 13:15 ` redi at gcc dot gnu.org 2021-06-24 19:25 ` ppalka at gcc dot gnu.org
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