https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105926
Bug ID: 105926
Summary: Using a spaceship operator on an optional of a type
derived from optional causes infinite constraint
recursion
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: ville.voutilainen at gmail dot com
Target Milestone: ---
Testcase:
#include <optional>
struct oink : std::optional<int> {
};
bool operator<(const oink&, const oink) {return false;}
bool operator>(const oink&, const oink) {return true;}
bool operator<=(const oink&, const oink) {return false;}
bool operator>=(const oink&, const oink) {return true;}
bool operator==(const oink&, const oink) {return false;}
bool operator!=(const oink&, const oink) {return true;}
int main()
{
oink a;
std::optional<oink> b;
b <=> a;
}
Ends up, eventually, with..
error: satisfaction of atomic constraint 'requires(const typename
std::remove_reference<_Tp>::type& __t, const typename
std::remove_reference<_Arg>::type& __u) {{__t < __u} -> decltype(auto)
[requires std::__detail::__boolean_testable<<placeholder>, >];{__t > __u} ->
decltype(auto) [requires std::__detail::__boolean_testable<<placeholder>,
>];{__t <= __u} -> decltype(auto) [requires
std::__detail::__boolean_testable<<placeholder>, >];{__t >= __u} ->
decltype(auto) [requires std::__detail::__boolean_testable<<placeholder>,
>];{__u < __t} -> decltype(auto) [requires
std::__detail::__boolean_testable<<placeholder>, >];{__u > __t} ->
decltype(auto) [requires std::__detail::__boolean_testable<<placeholder>,
>];{__u <= __t} -> decltype(auto) [requires
std::__detail::__boolean_testable<<placeholder>, >];{__u >= __t} ->
decltype(auto) [requires std::__detail::__boolean_testable<<placeholder>, >];}
[with _Up = oink; _Tp = oink]' depends on itself
302 | = requires(const remove_reference_t<_Tp>& __t,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
303 | const remove_reference_t<_Up>& __u) {
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
304 | { __t < __u } -> __boolean_testable;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
305 | { __t > __u } -> __boolean_testable;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
306 | { __t <= __u } -> __boolean_testable;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
307 | { __t >= __u } -> __boolean_testable;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
308 | { __u < __t } -> __boolean_testable;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
309 | { __u > __t } -> __boolean_testable;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
310 | { __u <= __t } -> __boolean_testable;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
311 | { __u >= __t } -> __boolean_testable;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
312 | };
The relevant bit being "satisfaction of atomic constraint foo depends on
itself".
