Regression - arrays are totally broken (SDK 4.1.2)

var arr = ["A", "B"];
arr.toString();

Gives

Error: Unhandled Exception
Exception: UnexpectedTypeException: Expected Number/Float/Long/Double/Char, given Number/Array

var arr = ["A", "B"];
for (var i = 0; i < arr.size(); i++) {
    arr[i];
}

Gives

Error: Unhandled Exception
Exception: UnexpectedTypeException: Expected Number/Float/Boolean/Long/Double, given Object

var arr = new Lang.Array();
arr.add("A");

Gives

Error: Unhandled Exception
Exception: UnexpectedTypeException: Expected Array, given String

SDK version 4.1.2.