[Bug c++/102465] New: Inaccessible operator == breaks child class with spaceship operator

[fchelnokov at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102465

            Bug ID: 102465
           Summary: Inaccessible operator == breaks child class with
                    spaceship operator
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

Below code is valid:
```
#include <compare>

struct A { 
    std::strong_ordering operator <=>(const A &) const = default;
    bool operator==(int) const;
};

struct B : A { 
    virtual std::strong_ordering operator <=>(const B &) const noexcept =
default;
};

B b; //GCC error here
```
but GCC prints an error compiling it. Demo: https://gcc.godbolt.org/z/584nhfxxs

It shall just delete `operator ==` in B.