This code fails compilation with the following errors:

   foo.d(5): template A() is used as a type
   foo.d(5): variable result voids have no value
   foo.d(6): cannot implicitly convert void to A

The code is:

   struct A ()
   {
      static A opCall ()
      {
         A result;
         return result;
      }
   }

   struct B ()
   {
      .A! () a ()
      {
         return .A! () ();
      }
   }

   B! () x;

I believe that this code is correct.