coverage for negative packed array indices

test/basic/flatten.sv

@@ -56,3 +56,18 @@ endmodule
 `CASE(D2, [3:5][2:6], 3, 2)
 `CASE(D3, [3:5][6:2], 3, 2)
 `CASE(D4, [5:3][2:6], 3, 2)
+
+`CASE(E1, [1:-1][4:0], -1, 0)
+`CASE(E2, [-1:1][0:4], -1, 0)
+`CASE(E3, [-1:1][4:0], -1, 0)
+`CASE(E4, [1:-1][0:4], -1, 0)
+
+`CASE(F1, [1:-1][1:-3], -1, -3)
+`CASE(F2, [-1:1][-3:1], -1, -3)
+`CASE(F3, [-1:1][1:-3], -1, -3)
+`CASE(F4, [1:-1][-3:1], -1, -3)
+
+`CASE(G1, [2:0][-6:-10], 0, -10)
+`CASE(G2, [0:2][-10:-6], 0, -10)
+`CASE(G3, [0:2][-6:-10], 0, -10)
+`CASE(G4, [2:0][-10:-6], 0, -10)