https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94162
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- It isn't clear to me what exactly disallows it, perhaps http://eel.is/c++draft/class.spaceship#2.2 ? For auto return type http://eel.is/c++draft/class.spaceship#4 defines what return type it should have. If the explicit return type isn't auto, but is one of the std::{strong,weak,partial}_ordering, we don't ICE and accept it, should we and what behavior should it have? #include <compare> struct S { float a; std::strong_ordering operator<=>(const S&) const = default; }; bool b = S{} < S{}; struct T { std::partial_ordering operator<=>(const T&) const = default; }; bool c = T{} < T{}; For S, the auto return type would be std::partial_ordering and in the generated body we just assume the floats will not be unordered. So, for bool, shall it be accepted and handled some way, or shall it be deleted, or result in immediate error (ill-formed)? What about even weirder types (say float or int * or some arbitrary class)?
