https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111016
Bug ID: 111016
Summary: Confusing "used in its own initializer" for
non-dependent ad-hoc constraint
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: ed at catmur dot uk
Target Milestone: ---
#include <concepts>
struct S { int i; };
static_assert(requires(S s) { requires std::destructible<decltype(s.i)>; });
In file included from <source>:1:
include/c++/14.0.0/concepts:148:13: required for the satisfaction of
'destructible<decltype (s.i)>'
include/c++/14.0.0/concepts:148:38: error: the value of
'std::__detail::__destructible<decltype (s.i)>' is not usable in a constant
expression
148 | concept destructible = __detail::__destructible<_Tp>;
| ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
include/c++/14.0.0/concepts:127:22: note:
'std::__detail::__destructible<decltype (s.i)>' used in its own initializer
127 | constexpr bool __destructible = __destructible_impl<_Tp>;
| ^~~~~~~~~~~~~~
Obviously this is IFNDR, but it would be nice to emit a diagnostic which gives
some better clue to what is going on (e.g. "warning: constraint is
non-dependent"). Unfortunately both clang and MSVC accept with no diagnostic,
making this look like a gcc bug.
