non-defaulted operator <=> doesn't generate == and != in C++20

Question

I\'m running into a strange behavior with the new spaceship operator <=> in C++20. I\'m using Visual Studio 2019 compiler with /std:c++latest

Answer 1

The other answers explain really well why the language is like this. I just wanted to add that in case it's not obvious, it is of course possible to have a user-provided operator<=> with a defaulted operator==. You just need to explicitly write the defaulted operator==:

struct X
{
    int Dummy = 0;
    auto operator<=>(const X& other) const
    {
        return Dummy <=> other.Dummy;
    }
    bool operator==(const X& other) const = default;
};