[Bug c++/116289] [13 regression] Can't apply decltype to comparison operators created by spaceship operator for local classes

[fchelnokov at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116289

--- Comment #8 from Fedor Chelnokov <fchelnokov at gmail dot com> ---
Thanks for quick fix. 

A workaround for this issue in GCC 13.3 is to declare spaceship operator as
constexpr:
```
int main() {
    struct A {
        int x = 0;
        constexpr auto operator<=>(const A &) const = default;
    };
    decltype(A{} < A{}) y;
}
```
Online demo: https://gcc.godbolt.org/z/Pfq8hb5s3