%Warning-UNOPTFLAT: t/t_unopt_converge.v:19:11: Signal unoptimizable: Circular combinational logic: 'x'
   19 |    output x;    
      |           ^
                    ... For warning description see https://verilator.org/warn/UNOPTFLAT?v=latest
                    ... Use "/* verilator lint_off UNOPTFLAT */" and lint_on around source to disable this message.
                    t/t_unopt_converge.v:19:11:      Example path: x
                    t/t_unopt_converge.v:23:9:      Example path: ASSIGNW
                    t/t_unopt_converge.v:19:11:      Example path: x
%Error: Exiting due to