%Error: t/t_hier_block0_bad.v:21:11: 'sub0' has hier_block metacomment, hierarchical Verilation supports only integer/floating point/string and type param parameters
                                   : ... note: In instance 't'
   21 |    sub0 #(UNPACKED) i_sub0(.clk(clk), .in(8'(count)), .out(out0));
      |           ^~~~~~~~
        ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
%Error: t/t_hier_block0_bad.v:62:41: Cannot access non-port symbols inside hierarchical block
                                   : ... note: In instance 't.i_sub0'
   62 |       $display("%m: i_sub.x: %d", i_sub.x);
      |                                         ^
%Error: t/t_hier_block0_bad.v:26:50: Cannot access non-port symbols inside hierarchical block
                                   : ... note: In instance 't'
   26 |       $display("%d i_sub0.ff: %d", count, i_sub0.ff);
      |                                                  ^~
%Error: t/t_hier_block0_bad.v:27:63: Cannot access scope inside hierarchical block
   27 |       $display("%d i_sub0.i_sub.out: %d", count, i_sub0.i_sub.out);
      |                                                               ^~~
%Error: Exiting due to