https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107325
Bug ID: 107325
Summary: Defaulted operator<=> with a non-comparison-category
return type is not deleted
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Keywords: accepts-invalid
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: de34 at live dot cn
Target Milestone: ---
In this example, the operator<=> overload for Bar<int> is deleted according to
[class.spaceship] (1.3) and (2.2), and thus decltype(Bar<int>{} <=> Bar<int>{})
is ill-formed.
But gcc currently accepts it (Godbolt link: https://godbolt.org/z/z1bPbGPx7).
#include <compare>
template<class Ord>
struct Bar {
friend Ord operator<=>(Bar, Bar) = default;
};
using SO = decltype(Bar<std::strong_ordering>{} <=>
Bar<std::strong_ordering>{}); // OK
using WO = decltype(Bar<std::weak_ordering>{} <=> Bar<std::weak_ordering>{});
// OK
using PO = decltype(Bar<std::partial_ordering>{} <=>
Bar<std::partial_ordering>{}); // OK
using I = decltype(Bar<int>{} <=> Bar<int>{}); // This should be rejected.
