Proposed resolution (approved by CWG 2024-10-11):

Change in 12.4.1 [over.oper.general] paragraph 7 as follows, removing the bullets:

An operator function shall either

• be a member function or
• be a non-member function that has have at least one non-object parameter or implicit object parameter whose type is a class, a reference to a class, an enumeration, or a reference to an enumeration.

(From submission #600.)

With the introduction of explicit object member functions, the restrictions on operator functions became inconsistent. Subclause 12.4.1 [over.oper.general] paragraph 7 specifies:

An operator function shall either

• be a member function or
• be a non-member function that has at least one non-object parameter whose type is a class, a reference to a class, an enumeration, or a reference to an enumeration.

Talking about non-object parameters in a bullet discussing non-member functions makes no sense. The following example ought to be prohibited, for consistency with operator==(int, int):

  struct B {
    bool operator==(this int, int);
    operator int() const;
  };