Why is this an issue?

A case item is unreachable because earlier wilcard items completely cover all of its possible values.

How to fix it

Code examples

Noncompliant code example

module fly;
  logic [2:0] a;
  initial begin
    casez (a)
      3'b10?:;
      3'b101:;
      default;
    endcase
  end
endmodule

Compliant solution

module fly;
  logic [2:0] a;
  initial begin
    casez (a)
      3'b10?:;
      3'b001:;
      default;
    endcase
  end
endmodule