var samples = [

    "[...a]",

    "[...[1]]",

    "[1, ...a, 2]",

    "[1, ...[2, 3], 4]",

    "[...[1], , ]",

    "[1, , ...[2]]",

    "[, 1, ...[2], ...[3], , 4, 5, , ]"

];

for (var sample of samples) {

    var source = "function f() {\n    return " + sample + ";\n}";

    eval(source);

    assertEq(f.toString(), source);

}