Array concatenation exception

[YiWen-y]

Version

Version: 3.0.0 (fea10bb7)

Execution steps

/.jsvu/jerry Testcase.js

Test case 1

var foo = function(it) {
    var a = [...it, , ];
    print(a);
    print(a.length);
};
var Parameter0 = [1, 2];
foo(Parameter0);

Output 1

1,2
2

Expected behavior

1,2,
3

Test case 2

var foo = function(it) {
    var arr = [ , ];
    var a = it.concat(arr);
    print(a);
    print(a.length);
};
var Parameter0 = [1, 2];
foo(Parameter0);

Output 2

1,2,
3

Description

I tested on multiple JS engines, test case 1 and test case 2 have the same semantics, they should have the same output. But jerry outputs abnormal results when executing test case 1.

[YiWen-y]

The author replied in Array concatenation exception #5026