int
foo (void)
{
  if (0)
    {
      static union
      {
        long i;
        char c[8];
      } u;
      u.i = 0x01020304;
      return u.c[0] == 0x01 && u.c[1] == 0x02;
    }
  return 0;
}

ICEs at -g -O0 in dwarf2out_finish, because the UNION_TYPE has TYPE_CONTEXT set, but not to some FUNCTION_DECL, but to BLOCK (that has been optimized out).