[Bug c++/108759] New: "mandatory copy elision" not implemented during constant evaluation redux

[herring at lanl dot gov]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108759

            Bug ID: 108759
           Summary: "mandatory copy elision" not implemented during
                    constant evaluation redux
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: herring at lanl dot gov
  Target Milestone: ---

Extending the test case in (the invalid) #94537 to have a user-provided
destructor does not cause the "mandatory copy elision" to take place even
though the implementation is no longer permitted to introduce a temporary:

  struct A;
  extern const A a;
  struct A {
    bool special=this==&a;
    constexpr ~A() {}
  };
  constexpr A get() {return {};}  // or "return A();"
  constexpr A a=get();
  static_assert(a.special);