This would assume support for Generics of type Array (A generic declaration induces a family of declarations, one for each set of actual type parameters provided in the program).
For example a string Array could be declared as:
var arr : Array = new Array();
// then only elements of type 'string' could be added to 'arr'
arr = "hello";
// using elements other than of type 'string' would trigger compile time errors:
arr = 43;