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From: "ensadc at mailnesia dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/95310] New: [concepts] Unrelated template parameters printed in diagnostic Date: Mon, 25 May 2020 08:46:11 +0000 [thread overview] Message-ID: <bug-95310-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95310 Bug ID: 95310 Summary: [concepts] Unrelated template parameters printed in diagnostic Product: gcc Version: 10.0 Status: UNCONFIRMED Keywords: diagnostic Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: ensadc at mailnesia dot com CC: asutton at gcc dot gnu.org Target Milestone: --- https://godbolt.org/z/M8CVwc ==== template <class T> using iter_reference_t = decltype(*T{}); template <typename F> struct result { using type = iter_reference_t<F>; }; template <class Out, class T> concept indirectly_writable = requires(Out&& o, T&& t) { iter_reference_t<Out>(*o) = 0; }; static_assert(indirectly_writable<const int*, int&>); ==== <source>:13:15: error: static assertion failed 13 | static_assert(indirectly_writable<const int*, int&>); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <source>:13:15: note: constraints not satisfied <source>:10:9: required by the constraints of 'template<class Out, class T> concept indirectly_writable' <source>:10:31: in requirements with 'Out&& o', 'T&& t' [with F = const int*; T = int&; Out = const int*] <source>:11:29: note: the required expression 'decltype(*{})(*o)=0' is invalid 11 | iter_reference_t<Out>(*o) = 0; | ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~ cc1plus: note: set '-fconcepts-diagnostics-depth=' to at least 2 for more detail ==== Note "[with F = const int*; T = int&; Out = const int*]". The 'F = const int*;' part is spurious. When the template parameter of `result` has the same name as the parameter of the concept (which is the case I originally encountered), the output can be quite confusing. The expression 'decltype(*{})(*o)=0' also seems wrong. Might be related to bug 94862.
next reply other threads:[~2020-05-25 8:46 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-05-25 8:46 ensadc at mailnesia dot com [this message] 2020-05-27 14:12 ` [Bug c++/95310] " ppalka at gcc dot gnu.org 2020-10-13 19:39 ` redi at gcc dot gnu.org 2020-10-17 5:31 ` ensadc at mailnesia dot com 2020-10-20 3:20 ` ppalka at gcc dot gnu.org
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