Why is this an issue?

For a non-ANSI instance port or function body port declaration, the port I/O specifies a signing keyword but the actual data type of the port does not permit that signing to take effect.

How to fix it

Code examples

Noncompliant code example

module fly(a);
  input unsigned a;
  int a;
endmodule

Compliant solution

module fly(a);
  input a;
  int a;
endmodule