Why can't parameter class typedefs be used in variable declarations?

In reply to Steve Roe:

This small example worked for me.

class env #(type P, type V);

  type(V::bus_loopback_vif_t) bus_loopback_direct_vif;

endclass

module top;
class B;
   typedef int bus_loopback_vif_t;
endclass // B
   env#(int,B) e;
endmodule

Can show a small example that fails for you.