An implicitly created net is not referenced elsewhere in the design. This is often a typo in the name and not intentional.
module fly(output x); assign x = 1; endmodule module top; logic typo; fly fly1(typa); // Noncompliant: 'typa' instead of 'typo' endmodule
module fly(output x); assign x = 1; endmodule module top; logic typo; fly fly1(typo); endmodule