[Bug c++/80460] Incorrect fallthrough warning after [[noreturn]] function inside always-true conditional

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80460

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
But even that is not enough for

  switch (i) 
    {   
    case 0:
      goto X;
      if (0) // nowarn
X:
        nop (); 
      else
        die (); 
    case 1:; 
      i++;
    }

because we need to remember whether the then branch contained any labels.