How many lines does one need to break VCS? Not much.

module tb;
  logic a = 0;
  logic b = 0;
  logic bb = 0;
  logic [1:0] c;
  
  function automatic logic foo(logic x, logic y);
    return x && y;
  endfunction
  
  always_comb begin
    c = 0;
    unique0 if (a) begin
      c = 1;
    end else if (foo(b, bb)) begin
      c = 2;
    end else begin
      c = 3;
    end
  end
  
  initial begin
    #1;
    a <= 1;
    b <= 0;
    bb <= 0;
    #1;
    a <= 0;
    b <= 1;
    bb <= 1;
    #1;
  end
  
  initial begin
    $monitor("%t : %b %b %b %0d", $time(), a, b, bb, c);
  end
  
endmodule

Output:

                   0 : 0 0 0 0
                   1 : 1 0 0 1
                   2 : 0 1 1 0