%Warning-WIDTH: t/t_func_bad_width.v:12: Operator FUNCREF 'MUX' expects 40 bits on the Function Argument, but Function Argument's VARREF 'in' generates 39 bits.
      out = MUX (in);
            ^~~
                ... Use "/* verilator lint_off WIDTH */" and lint_on around source to disable this message.
%Warning-WIDTH: t/t_func_bad_width.v:12: Operator ASSIGN expects 4 bits on the Assign RHS, but Assign RHS's FUNCREF 'MUX' generates 32 bits.
      out = MUX (in);
          ^
%Error: Exiting due to
