[Bug c++/123642] New: [reflection] error in case of splice with reflection of an anonymous union member

[valentin.yukhymenko at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123642

            Bug ID: 123642
           Summary: [reflection] error in case of splice with reflection
                    of an anonymous union member
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: valentin.yukhymenko at gmail dot com
  Target Milestone: ---

Code like this fails to compile.

```
struct foo {
  int i;
  union {
    int a;
    long b;
  };
};

int main() {
  constexpr foo bar { .i = 11, .a = 1 };
  static_assert(bar.a == 1);

  static_assert(bar.[:^^foo::a:] == 1); 
  // ERROR: class 'foo' not derived from '(anonymous union at <source>:3:3)'

  static_assert(bar.*&[:^^foo::a:] == 1); 
  // NO ERROR
}

```

https://compiler-explorer.com/z/jYdWWTGTs