With the following .cpp code, VAX is not able to provide any suggestions for members in anon1.  When I manually type the .a, it puts the red squiggly under it.
struct
{
  struct 
  {
    char a;
    int b;
  }anon1;
}anon;
void main( void )
{
  anon.anon1.a = 'a';
}
VA_X.dll file version 10.3.1534.0  built 2006.09.02
VS6 English