Why is this an issue?

A case statement that is marked unique or priority has a default item. Using unique or priority asserts that the case items fully cover all possible inputs, so the default item should never be hit.

How to fix it

Code examples

Noncompliant code example

module m;
  logic [2:0] a;
  initial begin
    unique case (a)
      1:;
      2:;
      default; // Noncompliant
    endcase
  end
endmodule

Compliant solution

module m;
  logic [2:0] a;
  initial begin
    unique case (a)
      1:;
      2:;
    endcase
  end
endmodule