Author Name: Geoff Barrett
Original Redmine Issue: 1395 from https://www.veripool.org

The following code produces no warnings:

module unused_vars (
  input var logic ck,
  output var logic c
);

logic d, q;

always_ff @(posedge ck) q <= d;
always_comb d = q;

always_comb c = '0;

endmodule : unused_vars

The combination of UNUSED and UNOPTFLAT means (I think) that we will always get a warning if signals are not either in the cone of an output or a nonblocking assignment. However, d and q are only used by each other and can be eliminated from the module and it would be very useful to get a warning about this.