[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union

["vlad at petric dot cc" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551

--- Comment #7 from Vlad Petric <vlad at petric dot cc> ---
Ok, so the example that I started this bug with is not standard compliant
because it initialized different elements in a union with the constexpr
constructor.

The following does just one. I believe that the following is standard-compliant
code (though obviously I could be wrong)

And it generates a segfault.

struct A {
  union {
    long s;
    char d[4];
  };
  constexpr A (char x) : d("") { d[0] = x; }
};

A a{'a'};