%Error: t/t_inst_paren_bad.v:11:4: Non-interface used as an interface: 'sub'
                                 : ... Perhaps intended an instantiation but are missing parenthesis (IEEE 1800-2023 23.3.2)?
   11 |    sub sub_inst;   
      |    ^~~
%Warning-MULTITOP: t/t_inst_paren_bad.v:10:8: Multiple top level modules
                                            : ... Suggest see manual; fix the duplicates, or use --top-module to select top.
                   ... For warning description see https://verilator.org/warn/MULTITOP?v=latest
                   ... Use "/* verilator lint_off MULTITOP */" and lint_on around source to disable this message.
                                            : ... Top module 'sub'
    7 | module sub;
      |        ^~~
                                            : ... Top module 't'
   10 | module t( );
      |        ^
%Error: Exiting due to